Signal detection by means of supplemental information

ABSTRACT

A method of communicating information from a sensor concerning a received signal, comprising: responsive to receiving by at least one detecting sensor, during a defined time interval data indicative of an entire data of a frequency band received by it during the defined time interval, comprising at least one signal emitted at least one emitter, and to detecting of the emitted signal by the at least one detecting sensor, sending from the sensor assistance information corresponding to the detected emitted signal during the defined time interval, to at least one non-detecting sensor. This information can be utilized by the non-detecting sensor to perform an action with respect to data indicative of an entire data of the frequency band received by the non-detecting sensor during a corresponding defined time interval, the action corresponding to at least one emitted signal received by the non-detecting sensor during the corresponding defined time interval.

TECHNOLOGICAL FIELD

The presently disclosed subject matter relates to systems and methodsfor signal detection.

BACKGROUND

System architectures for signal detection are known in the art. Emittersmay emit electro-magnetic signals. Sensors may be capable of detectingemitted electro-magnetic signals, for example using known time- and/orspectral-based techniques. A plurality of sensors may be selected towork together as a group regarding a particular application. A systemcenter may receive transmissions of data from one or more of thesensors, and may use this information to perform an application task. Itmay be the case that when an insufficient number of sensors in the groupreport in their transmission that they detected a particular signalduring a particular time interval, the system center may haveinsufficient information available to be able to perform the applicationtask.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the presently disclosed subjectmatter, there is provided a method of communicating information from asensor concerning a received signal, comprising:

-   -   (a) responsive to receiving by at least one detecting sensor,        during a defined time interval, data indicative of an entire        data of a frequency band received by the at least one detecting        sensor during the defined time interval, comprising at least one        signal emitted by at least one emitter, and to detecting of the        at least one emitted signal by the at least one detecting        sensor,    -   sending from the at least one detecting sensor an assistance        information corresponding to the at least one emitted signal        detected by the at least one detecting sensor during the defined        time interval, to at least one non-detecting sensor,    -   wherein the assistance information is capable of being utilized        by the at least one non-detecting sensor to perform an action        with respect to data indicative of an entire data of the        frequency band received by the at least one non-detecting sensor        during a corresponding defined time interval, the action        corresponding to the at least one emitted signal received by the        at least one non-detecting sensor during the corresponding        defined time interval.

In accordance with a second aspect of the presently disclosed subjectmatter, there is further provided a method of performing an actionassociated with a received signal, comprising:

-   -   (a) receiving by at least one non-detecting sensor, an        assistance information from at least one detecting sensor,        -   wherein the assistance information was sent by the at least            one detecting sensor, responsive to receiving by the at            least one detecting sensor, during a defined time interval,            data indicative of an entire data of a frequency band            received by the at least one detecting sensor during the            defined time interval, comprising at least one signal            emitted by at least one emitter, and to detecting of the at            least one emitted signal by the at least one detecting            sensor,        -   wherein the assistance information corresponds to the at            least one detected emitted signal to at least one            non-detecting sensor during the defined time interval; and    -   (b) performing the action with respect to data indicative of an        entire data of the frequency band received by the at least one        non-detecting sensor during a corresponding defined time        interval, the action corresponding to the at least one emitted        signal received by the at least one non-detecting sensor during        the corresponding defined time interval.

In accordance with a third aspect of the presently disclosed subjectmatter, there is yet further provided a non-transitory program storagedevice readable by a computer tangibly embodying computer readableinstructions executable by the computer to perform a method ofcommunicating information from a sensor concerning a received signal;the method comprising:

-   -   (a) responsive to receiving by at least one detecting sensor,        during a defined time interval data indicative of an entire data        of a frequency band received by the at least one detecting        sensor during the defined time interval, comprising at least one        signal emitted by at least one emitter, and to detecting of the        at least one emitted signal by the at least one detecting        sensor,    -   sending from the at least one detecting sensor an assistance        information corresponding to the at least one emitted signal        detected by the at least one detecting sensor during the defined        time interval, to at least one non-detecting sensor,    -   wherein the assistance information is capable of being utilized        by the at least one non-detecting sensor to perform an action        with respect to data indicative of an entire data of a frequency        band received by the at least one non-detecting sensor during a        corresponding defined time interval, the action corresponding to        the at least one emitted signal received by the at least one        non-detecting sensor during the corresponding defined time        interval.

In accordance with a fourth aspect of the presently disclosed subjectmatter, there is yet further provided a non-transitory program storagedevice readable by a computer tangibly embodying computer readableinstructions executable by the computer to perform a method ofperforming an action associated with a received signal; the methodcomprising:

-   -   (a) receiving by at least one non-detecting sensor, an        assistance information from at least one detecting sensor,        -   wherein the assistance information was sent by the at least            one detecting sensor, responsive to receiving by the at            least one detecting sensor, during a defined time interval,            data indicative of an entire data of a frequency band            received by the at least one detecting sensor during the            defined time interval, comprising at least one signal            emitted by at least one emitter, and to detecting of the at            least one emitted signal by the at least one detecting            sensor,        -   wherein the assistance information corresponds to the at            least one detected emitted signal to at least one            non-detecting sensor during the defined time interval; and    -   (b) performing the action with respect to data indicative of an        entire data of the frequency band received by the at least one        non-detecting sensor during a corresponding defined time        interval, the action corresponding to the at least one emitted        signal received by the at least one non-detecting sensor during        the corresponding defined time interval.

In accordance with a fifth aspect of the presently disclosed subjectmatter, there is yet further provided a system capable of communicatinginformation concerning a received signal, comprising: a sensor, thesensor comprising a processing circuitry and configured to:

-   -   (a) responsive to receiving by at least one detecting sensor,        during a defined time interval, data indicative of an entire        data of a frequency band received by the at least one detecting        sensor during the defined time interval, comprising at least one        signal emitted by at least one emitter, and to detecting of the        at least one emitted signal by the at least one detecting        sensor,    -   send from the at least one detecting sensor assistance        information corresponding to the at least one emitted signal        detected by the at least one detecting sensor during the defined        time interval, to at least one non-detecting sensor,    -   wherein the assistance information is capable of being utilized        by the at least one non-detecting sensor to perform an action        with respect to data indicative of an entire data of a frequency        band received by the at least one non-detecting sensor during a        corresponding defined time interval, the action corresponding to        the at least one emitted signal received by the at least one        non-detecting sensor during the corresponding defined time        interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the assistanceinformation does not comprise the entire data of the frequency bandreceived by the at least one detecting sensor during the defined timeinterval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the assistanceinformation comprises at least one instruction for saving of datareceived by the at least one non-detecting sensor during thecorresponding defined time interval, indicative of the at least oneemitted signal detected by the at least one detecting sensor during thedefined time interval, and wherein performing the action comprises:saving of data, and sending at least a portion of the saved data to asystem center when communication to the system center is available.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein performing theaction comprises extracting, from the data indicative of the entire dataof a frequency band received by the at least one non-detecting sensorduring the corresponding defined time interval, data indicative of theat least one emitted signal received by the at least one non-detectingsensor during the corresponding defined time interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the assistanceinformation comprises data indicative of an entire received data sampleat the at least one detecting sensor corresponding to the at least oneemitted signal detected by the at least one detecting sensor.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the dataindicative of the entire received data sample comprises data indicativeof an entire received data sample at the at least one detecting sensorcorresponding to at least one frequency of the at least one detectedemitted signal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the dataindicative of the entire received data sample comprises data indicativeof an entire received data sample at the at least one detecting sensorcorresponding to sample times of the at least one detected emittedsignal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the assistanceinformation is sent also to at least one other detecting sensor in aselected sensor group.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein extracting dataindicative of the at least one emitted signal comprises calculatingdifference data, based on the data indicative of the entire receiveddata sample at the at least one detecting sensor corresponding to the atleast one detected emitted signal, and on the data indicative of theentire data of the frequency band received by the at least onenon-detecting sensor during the corresponding defined time interval, thedifference data constituting data indicative of the at least one emittedsignal received by the at least one non-detecting sensor during thecorresponding defined time interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, the system furtherconfigured to:

-   -   prior to performing step (a) of the fifth aspect of the        presently disclosed subject matter, perform the following:    -   (b) responsive to receiving by the at least one detecting        sensor, during a defined time interval, data indicative of the        entire data of the frequency band received by the at least one        detecting sensor during the defined time interval, the entire        data comprising the at least one signal emitted by the at least        one emitter, and to detecting of the at least one emitted signal        by the at least one detecting sensor, sending by the at least        one detecting sensor, during the defined time interval, to at        least one of other sensors in a selected sensor group, first        information indicative of the at least one detected emitted        signal, wherein the first information is indicative of the        Signal to Noise Ratio (SNR) of the at least one detected emitted        signal; and    -   (c) responsive to receiving first information from the at least        one of other sensors in the selected sensor group, indicative of        detection of the at least one detected emitted signal by the at        least one of other sensors, determining which assistance        information, if any, should be sent to each one of at least one        of other sensors in the selected sensor group.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein step (c) of thefifth aspect of the presently disclosed subject matter furthercomprises: responsive to the detecting sensor receiving the at least onedetected emitted signal at a highest Signal to Noise Ratio, determiningthat step (a) of the fifth aspect of the presently disclosed subjectmatter should be performed in respect of each sensor in the selectedsensor group that did not send first information indicative of detectionof the at least one detected emitted signal, each sensor constituting atleast one non-detecting sensor.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the firstinformation sent by at least one detecting sensor to at least one ofother sensors comprises a pulse parameters set.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein a requiredcommunication bandwidth for the assistance information is substantiallysmaller than a communication bandwidth required when sending the entiredata of a frequency band received by the at least one detecting sensorduring the defined time interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the requiredcommunication bandwidth for the assistance information is less than 10percent of that required when sending the entire data of a frequencyband received by the at least one detecting sensor during the definedtime interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least onesignal emitted by at least one emitter is a non-coherent signal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the assistanceinformation comprises at least one set of parameter values correspondingto the least one detected emitted signal, wherein the extracting dataindicative of at the least one emitted signal comprises determining atleast a Time of Arrival (TOA) value of the at least one emitted signalat the at least one non-detecting sensor, the at least the Time ofArrival of the at least one emitted signal constituting data indicativeof at least one emitted signal received by the at least onenon-detecting sensor during the corresponding defined time interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least oneset of parameter values comprise at least: emitter frequency, a pulsewidth (PW), at least one Time of Arrival corresponding to the least onedetected emitted signal, a Pulse Repetition Interval (PRI) and a numberof pulses.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein determining atleast the Time of Arrival value comprises performing actions to filterout noise in the data indicative of an entire data of a frequency bandreceived by the at least one non-detecting sensor, thereby detecting theemitted signal, wherein the actions to filter out noise compriseintegrating a portion of the data indicative of an entire data of afrequency band that corresponds to at least one emitter frequency andwherein the portion of the data corresponds to time intervalscorresponding to the at least one detected emitted signal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the actions tofilter out noise comprise:

-   -   i) performing at least one first integration, of the data        indicative of the entire data of a frequency band received by        the at least one non-detecting sensor during the corresponding        defined time interval, the first integration based on a first        integration time interval and on the at least one emitter        frequency, thereby creating first data points, wherein the first        integration time interval corresponds to a defined percentage of        the Pulse Width; and    -   ii) determining whether the first data points comprise the data        indicative of at least one emitted signal received by the at        least one non-detecting sensor.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, the system furtherconfigured to:

-   -   iii) in response to determining that the first data points do        not comprise the data indicative of at least one emitted signal,        perform a second integration, of data indicative of the first        data points, based on a second integration time interval, and on        the at least one emitter frequency, thereby creating second data        points, wherein the second integration time interval corresponds        to the Pulse Repetition Interval; and    -   iv) determine that the second data points comprise the data        indicative of at least one emitted signal received by the at        least one non-detecting sensor.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the secondintegration is based on the number of pulses.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the secondintegration time interval is based on the Pulse Repetition Interval(PRI) and the number of pulses.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the secondintegration time interval is equal to the Pulse Repetition Interval(PRI) times (the number of pulses−1).

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the secondintegration is one of a Fourier Transform, a Discrete Fourier Transformand a Fast Fourier Transform.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the firstintegration time interval is equal to PW/2.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the firstintegration is one of a Fourier Transform, a Discrete Fourier Transform,a Fast Fourier Transform and a Finite Impulse Response (FIR).

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the dataindicative of the entire data of a frequency band received by the atleast one non-detecting sensor is multiplied by a window prior to step(i) of the fifth aspect of the presently disclosed subject matter.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, the system furtherconfigured to:

-   -   (v) set the second integration time interval to be equal to        Pulse Width,    -   (vi) select, from the data indicative of the entire data of a        frequency band received by the at least one non-detecting        sensor, a portion of the data which corresponds to a time that        is within a second time interval before at least one Time of        Arrival of the at least one emitted signal at the at least one        non-detecting sensor, and a third time interval after the at        least one Time of Arrival, constituting data indicative of the        entire data of a frequency band received by the at least one        non-detecting sensor during the corresponding defined time        interval;    -   (vii) perform at least one modified first integration, of the        portion of the data, the first integration based on a first        integration time interval and on at least one emitter frequency,        thereby creating modified first data points, wherein the first        integration time interval corresponds to the Pulse Width,        wherein first integrations are performed separately in respect        of each of the data indicative of the entire data of a frequency        band received by the at least one non-detecting sensor, wherein        the modified first data points constitute first data points; and    -   (viii) repeat steps (iii) and (iv) of the fifth aspect of the        presently disclosed subject matter,    -   thereby determining a second Time of Arrival value of the at        least one emitted signal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the second Timeof Arrival value is more accurate than the Time of Arrival value.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the size of theat least one parameter set for one emitter and for one dwell is lessthan 1000 bits.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least onesignal emitted by at least one emitter is a coherent signal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the extractingof the data indicative of the at least one emitted signal by the atleast one non-detecting sensor can be performed without the at least onenon-detecting sensor being required to buffer data samples untilcommunication to the system center is available.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the dataindicative of the entire data of a frequency band received by the atleast one non-detecting sensor comprises the entire data of a frequencyband received by the at least one non-detecting sensor.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the sending ofthe assistance information from the at least one detecting sensorcomprises at least one of: sending directly from the detecting sensor tothe non-detecting sensor, relaying via at least one other sensor, andrelaying via at least one system center.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least onedetecting sensor and at least one non-detecting sensor are comprised inat least one of an airborne vehicle, a balloon, a space-borne vehicle, aground station, a ground vehicle, and a water-borne vehicle.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least onesystem center is comprised in at least one of airborne vehicle, aballoon, a space-borne vehicle, a ground station, a ground vehicle, anda water-borne vehicle.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least oneemitter is one of: a radio transmitter equipment, a radar, and acommunication system.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the defined timeinterval is a dwell.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the action withrespect to data indicative of an entire data of the frequency bandreceived by the at least one non-detecting sensor during a correspondingdefined time interval may be utilized for calculating a location of theat least one emitter.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein step (a) of thefifth aspect of the presently disclosed subject matter is furtherperformed for at least a next defined time interval.

In accordance with a sixth aspect of the presently disclosed subjectmatter, there is yet further provided a system capable of performing anaction associated with a received signal, comprising: a sensor, thesensor comprising a processing circuitry and configured to:

-   -   (a) receive by at least one non-detecting sensor, an assistance        information from at least one detecting sensor,    -   wherein the assistance information was sent by the at least one        detecting sensor, responsive to receiving by the at least one        detecting sensor, during a defined time interval, data        indicative of an entire data of a frequency band received by the        at least one detecting sensor during the defined time interval,        comprising at least one signal emitted by at least one emitter,        and to detecting of the at least one emitted signal by the at        least one detecting sensor,    -   wherein the assistance information corresponds to the at least        one detected emitted signal to the at least one detecting sensor        during the defined time interval; and    -   (b) perform the action with respect to data indicative of an        entire data of the frequency band received by the at least one        non-detecting sensor during a corresponding defined time        interval, the action corresponding to the at least one emitted        signal received by the at least one non-detecting sensor during        the corresponding defined time interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the assistanceinformation does not comprise the entire data of the frequency bandreceived by the at least one detecting sensor during the defined timeinterval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the assistanceinformation comprises at least one instruction for saving of datareceived by the at least one non-detecting sensor during thecorresponding defined time interval, indicative of the at least oneemitted signal detected by the at least one detecting sensor during thedefined time interval, and wherein performing the action comprises:saving of data, and sending at least a portion of the saved data to asystem center when communication to the system center is available.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein performing theaction comprises extracting, from the data indicative of the entire dataof a frequency band received by the at least one non-detecting sensorduring the corresponding defined time interval, data indicative of theat least one emitted signal received by the at least one non-detectingsensor during the corresponding defined time interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the assistanceinformation comprises data indicative of an entire received data sampleat the at least one detecting sensor corresponding to the at least oneemitted signal detected by the at least one detecting sensor.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the dataindicative of the entire received data sample comprises data indicativeof an entire received data sample at the at least one detecting sensorcorresponding to at least one frequency of the at least one detectedemitted signal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the dataindicative of the entire received data sample comprises data indicativeof an entire received data sample at the at least one detecting sensorcorresponding to sample times of the at least one detected emittedsignal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the assistanceinformation is sent also to at least one other detecting sensor in aselected sensor group.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein extracting dataindicative of the at least one emitted signal comprises calculatingdifference data, based on the data indicative of the entire receiveddata sample at the at least one detecting sensor corresponding to the atleast one detected emitted signal, and on the data indicative of theentire data of the frequency band received by the at least onenon-detecting sensor during the corresponding defined time interval, thedifference data constituting data indicative of the at least one emittedsignal received by the at least one non-detecting sensor during thecorresponding defined time interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the firstinformation sent by at least one detecting sensor to at least one ofother sensors comprises a pulse parameters set.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein a requiredcommunication bandwidth for the assistance information is substantiallysmaller than a communication bandwidth required when sending the entiredata of a frequency band received by the at least one detecting sensorduring the defined time interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the requiredcommunication bandwidth for the assistance information is less than 10percent of that required when sending the entire data of a frequencyband received by the at least one detecting sensor during the definedtime interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least onesignal emitted by at least one emitter is a non-coherent signal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the assistanceinformation comprises at least one set of parameter values correspondingto the least one detected emitted signal, wherein the extracting dataindicative of the at least one emitted signal comprises determining atleast a Time of Arrival (TOA) value of the at least one emitted signalat the at least one non-detecting sensor, the at least the Time ofArrival of the at least one emitted signal constituting data indicativeof at least one emitted signal received by the at least onenon-detecting sensor during the corresponding defined time interval.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least oneset of parameter values comprises at least: emitter frequency, a pulsewidth (PW), at least one Time of Arrival corresponding to the least onedetected emitted signal, a Pulse Repetition Interval (PRI) and a numberof pulses.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein determining atleast the Time of Arrival value comprises performing actions to filterout noise in the data indicative of an entire data of a frequency bandreceived by the at least one non-detecting sensor, thereby detecting theemitted signal, wherein the actions to filter out noise compriseintegrating a portion of the data indicative of an entire data of afrequency band that corresponds to at least one emitter frequency andwherein the portion of the data corresponds to time intervalscorresponding to the at least one detected emitted signal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the actions tofilter out noise comprise:

-   -   i) performing at least one first integration, of the data        indicative of the entire data of a frequency band received by        the at least one non-detecting sensor during the corresponding        defined time interval, the first integration based on a first        integration time interval and on the at least one emitter        frequency, thereby creating first data points, wherein the first        integration time interval corresponds to a defined percentage of        the Pulse Width; and    -   ii) determining whether the first data points comprise the data        indicative of at least one emitted signal received by the at        least one non-detecting sensor.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, the system furtherconfigured to:

-   -   iii) in response to determining that the first data points do        not comprise the data indicative of at least one emitted signal,        perform a second integration, of data indicative of the first        data points, based on a second integration time interval, and on        the at least one emitter frequency, thereby creating second data        points, wherein the second integration time interval corresponds        to the Pulse Repetition Interval; and    -   iv) determine that the second data points comprise the data        indicative of at least one emitted signal received by the at        least one non-detecting sensor.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the secondintegration is based on the number of pulses.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the secondintegration time interval is based on the Pulse Repetition Interval(PRI) and the number of pulses.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the secondintegration time interval is equal to the Pulse Repetition Interval(PRI) times (the number of pulses−1).

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the secondintegration is one of a Fourier Transform, a Discrete Fourier Transformand a Fast Fourier Transform.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the firstintegration time interval is equal to PW/2.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the firstintegration is one of a Fourier Transform, a Discrete Fourier Transform,a Fast Fourier Transform and a Finite Impulse Response (FIR).

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the dataindicative of the entire data of a frequency band received by the atleast one non-detecting sensor is multiplied by a window prior to step(i) of the sixth aspect of the presently disclosed subject matter.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, the system furtherconfigured to:

-   -   (v) set the second integration time interval to be equal to        Pulse Width,    -   (vi) select, from the data indicative of the entire data of a        frequency band received by the at least one non-detecting        sensor, a portion of the data which corresponds to a time that        is within a second time interval before at least one Time of        Arrival of the at least one emitted signal at the at least one        non-detecting sensor, and a third time interval after the at        least one Time of Arrival, constituting data indicative of the        entire data of a frequency band received by the at least one        non-detecting sensor during the corresponding defined time        interval;    -   (vii) perform at least one modified first integration, of the        portion of the data, the first integration based on a first        integration time interval and on at least one emitter frequency,        thereby creating modified first data points, wherein the first        integration time interval corresponds to the Pulse Width,        wherein first integrations are performed separately in respect        of each of the data indicative of the entire data of a frequency        band received by the at least one non-detecting sensor, wherein        the modified first data points constitute first data points; and    -   (viii) repeat steps (iii) and (iv) of the sixth aspect of the        presently disclosed subject matter,    -   thereby determining a second Time of Arrival value of the at        least one emitted signal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the second Timeof Arrival value is more accurate than the Time of Arrival value.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the size of theat least one parameter set for one emitter and for one dwell is lessthan 1000 bits.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least onesignal emitted by at least one emitter is a coherent signal.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the extractingof the data indicative of the at least one emitted signal by the atleast one non-detecting sensor can be performed without the at least onenon-detecting sensor being required to buffer data samples untilcommunication to the system center is available.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the dataindicative of the entire data of a frequency band received by the atleast one non-detecting sensor comprises the entire data of a frequencyband received by the at least one non-detecting sensor.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the sending ofthe assistance information from the at least one detecting sensorcomprises at least one of: sending directly from the detecting sensor tothe non-detecting sensor, relaying via at least one other sensor,relaying via at least one system center.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least onedetecting sensor and at least one non-detecting sensor are comprised inat least one of an airborne vehicle, a balloon, a space-borne vehicle, aground station, a ground vehicle, and a water-borne vehicle.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least onesystem center is comprised in at least one of airborne vehicle, aballoon, a space-borne vehicle, a ground station, a ground vehicle, anda water-borne vehicle.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the at least oneemitter is one of: a radio transmitter equipment, a radar, and acommunication system.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the defined timeinterval is a dwell.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein the action withrespect to data indicative of an entire data of the frequency bandreceived by the at least one non-detecting sensor during a correspondingdefined time interval may be utilized for calculating a location of theat least one emitter.

In accordance with an embodiment of the presently disclosed subjectmatter, there is yet further provided a system, wherein step (a) of thesixth aspect of the presently disclosed subject matter is furtherperformed for at least a next defined time interval.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system capable of performing an actionassociated with a received signal, comprising: a sensor, the sensorcomprising a processing circuitry and configured to:

-   -   (a) responsive to receiving by at least one detecting sensor,        during a defined time interval, data indicative of an entire        responsive to receiving by at least one detecting sensor, during        a defined time interval, data indicative of an entire data of a        frequency band received by the at least one detecting sensor        during the defined time interval, comprising at least one signal        emitted by at least one emitter, and to detecting of the at        least one emitted signal by the at least one detecting sensor,    -   sending from the at least one detecting sensor assistance        information corresponding to the at least one emitted signal        detected by the at least one detecting sensor during the defined        time interval, to at least one system center,    -   wherein the assistance information is capable of being utilized        by the at least one system center to send second assistance        information to at least one non-detecting sensor,    -   wherein the second assistance information is capable of being        utilized by the at least one non-detecting sensor to perform an        action with respect to data indicative of an entire data of the        frequency band received by the at least one non-detecting sensor        during a corresponding defined time interval, the action        corresponding to the at least one emitted signal received by the        at least one non-detecting sensor during the corresponding        defined time interval.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the presently disclosed subject matter and to seehow it can be carried out in practice, examples will now be described,by way of non-limiting example only, with reference to the accompanyingdrawings, in which:

FIG. 1 illustrates a generalized example system architecture for signaldetection, in accordance with certain embodiments of the presentlydisclosed subject matter.

FIGS. 2A to 2F illustrate generalized examples of electro-magnetictransmissions received at a sensor, in accordance with certainembodiments of the presently disclosed subject matter.

FIGS. 3A to 3B are block diagrams schematically illustrating ageneralized example sensor in accordance with certain exemplaryembodiments of the presently disclosed subject matter.

FIGS. 4A to 4C illustrate a flowchart of a generalized example sequenceof operations carried out to provide assistance information betweensensors, in accordance with certain embodiments of the presentlydisclosed subject matter.

FIGS. 5A to 5B illustrate a flowchart of a generalized example sequenceof operations carried out to provide assistance information betweensensors, in accordance with certain embodiments of the presentlydisclosed subject matter.

FIG. 6 illustrates generalized example representations of types ofsignals, in accordance with certain embodiments of the presentlydisclosed subject matter.

FIG. 7A illustrates a flowchart of a generalized example sequence ofoperations carried out to provide assistance information betweensensors, in accordance with certain embodiments of the presentlydisclosed subject matter.

FIG. 7B illustrates generalized example representations of frequencybins, in accordance with certain embodiments of the presently disclosedsubject matter.

FIG. 8 illustrates a generalized example of arranging filtered datapoints, in accordance with certain embodiments of the presentlydisclosed subject matter.

FIG. 9A illustrates a generalized example of a signal in the timedomain, in accordance with certain embodiments of the presentlydisclosed subject matter.

FIG. 9B illustrates a generalized example of arranging filtered datapoints, in accordance with certain embodiments of the presentlydisclosed subject matter.

FIGS. 10A to 10D illustrate a generalized example of arranging filtereddata points, in accordance with certain embodiments of the presentlydisclosed subject matter.

FIG. 11 illustrates a generalized example of second data points, inaccordance with certain embodiments of the presently disclosed subjectmatter.

FIGS. 12A to 12B illustrate a flowchart of a generalized examplesequence of operations carried out to determine Time(s) of Arrival, inaccordance with certain embodiments of the presently disclosed subjectmatter.

DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings and descriptions set forth, identical reference numeralsindicate those components that are common to different embodiments orconfigurations.

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresently disclosed subject matter may be practiced without thesespecific details. In other instances, well-known methods, procedures,components, circuits and protocols have not been described in detail soas not to obscure the presently disclosed subject matter.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “maneuvering”, “steering”,“detecting”, “determining”, “deciding”, “instructing”, “calculating”,“providing”, “performing”, “working”, “receiving”, “communicating”,“sending”, “routing”, “identifying”, “measuring”, “processing”,“transmitting”, “reporting”, “executing”, “scanning”, “synchronizing”,“sampling”, “controlling”, “monitoring”, “analyzing”, “correlating”,“writing”, or the like, include action(s) and/or processes of a computerthat manipulate and/or transform data into other data, said datarepresented as physical quantities, e.g. such as electronic ormechanical quantities, and/or said data representing the physicalobjects. The term “computer” should be expansively construed to coverany kind of hardware-based electronic device with data processingcapabilities, including, by way of non-limiting example, a personalcomputer, a server, a computing system, a communication device, aprocessor or processing unit (e.g. digital signal processor (DSP), amicrocontroller, a microprocessor, a field programmable gate array(FPGA), an application specific integrated circuit (ASIC), etc.), anyother electronic computing device, including, by way of non-limitingexample, the processing circuitry therein, such as for example theprocessing circuitry 350 (further detailed herein with regard to FIG.3A), disclosed in the present application.

The operations in accordance with the teachings herein may be performedby a computer specially constructed for the desired purposes, or by ageneral-purpose computer specially configured for the desired purpose bya computer program stored in a non-transitory computer-readable storagemedium.

Embodiments of the presently disclosed subject matter are not describedwith reference to any particular programming language. It will beappreciated that a variety of programming languages may be used toimplement the teachings of the presently disclosed subject matter asdescribed herein.

The terms “non-transitory memory” and “non-transitory storage medium”used herein should be expansively construed to cover any volatile ornon-volatile computer memory suitable to the presently disclosed subjectmatter.

As used herein, the phrase “for example,” “such as”, “for instance” andvariants thereof describe non-limiting embodiments of the presentlydisclosed subject matter. Reference in the specification to “one case”,“some cases”, “other cases”, “one example”, “some examples”, “otherexamples” or variants thereof means that a particular described method,procedure, component, structure, feature or characteristic described inconnection with the embodiment(s) is included in at least one embodimentof the presently disclosed subject matter, but not necessarily in allembodiments. The appearance of the same term does not necessarily referto the same embodiment(s) or example(s).

Usage of conditional language, such as “may”, “might”, or variantsthereof should be construed as conveying that one or more examples ofthe subject matter may include, while one or more other examples of thesubject matter may not necessarily include, certain methods, procedures,components and features. Thus such conditional language is not generallyintended to imply that a particular described method, procedure,component or circuit is necessarily included in all examples of thesubject matter. Moreover, the usage of non-conditional language does notnecessarily imply that a particular described method, procedure,component or circuit is necessarily included in all examples of thesubject matter.

It is appreciated that certain embodiments, methods, procedures,components or features of the presently disclosed subject matter, whichare, for clarity, described in the context of separate embodiments orexamples, may also be provided in combination in a single embodiment orexamples. Conversely, various embodiments, methods, procedures,components or features of the presently disclosed subject matter, whichare, for brevity, described in the context of a single embodiment, mayalso be provided separately or in any suitable sub-combination.

It should also be noted that each of the figures herein, and the textdiscussion of each figure, describe one aspect of the presentlydisclosed subject matter in an informative manner only, by way ofnon-limiting example, for clarity of explanation only. It will beunderstood that that the teachings of the presently disclosed subjectmatter are not bound by what is described with reference to any of thefigures or described in other documents referenced in this application.

It should also be noted that, in the presently disclosed subject matter,phrases such as “data indicative of the detected signal”, “dataindicative of the entire data of a frequency band received”, and thelike, are used in some cases. This usage is done, among other purposes,to clarify that, in some cases, receiving, processing, storing orsaving, sending etc. may not be performed on all of a particular set ofdata, but rather only a portion of the data.

Bearing this in mind, attention is now drawn to FIG. 1, illustrating anexample system architecture 100 for signal detection, in accordance withcertain embodiments of the presently disclosed subject matter. There areshown P emitters 120, 130, where P can be one or more. These emitelectro-magnetic signals 142, 143, for example in the RF frequencyrange. Non-limiting examples of such emitters may be radio transmitterequipment, or radar or communication systems. These emitters may belocated on, or associated with, platforms such airborne vehicles,balloons, space-borne vehicles, ground station, ground vehicles, andwater-borne vehicles, these being non-limiting examples. One example ofan airborne vehicle is an aircraft. Some examples of an space-bornevehicle are a satellite or a spacecraft. Another example of anspace-borne vehicle is a satellite. One example of a ground vehicle is atruck. One example of a water-borne vehicle is a ship. Each emitter 120,130 may in some cases emit electro-magnetic signals 142, 143 at afrequency different than that of other emitters, during a given timeframe.

There are further shown R sensors 105, 110, 115. R is at least two. Insome cases, R may be 3 or 4. These sensors are capable of detectingemitted electro-magnetic signals 142, 143, for example using known time-and/or spectral-based techniques. These sensors may be located on, orassociated with, platforms such as airborne vehicles, balloons,space-borne vehicles, ground systems, ground vehicles, and water-bornevehicles, these being non-limiting examples. A plurality of sensors maybe selected to work together regarding the particular application, andmay be configured to be aware of each other, and to be able tocommunicate with each other, for example in order to jointly provideinformation for use in a particular application. Such sensors may bereferred to as a selected sensor group. The utilization of multiplesensors that are capable of detecting emitted signals may be useful invarious applications. In the currently disclosed subject matter,geo-location will be described, as one non-limiting example application.Note that in some examples, a particular sensor 105 may belong to one ormore different selected sensor groups, depending on the configuration ofthe system—which in turn may be a function of the particularapplication. Note also, that in some examples, more than one of thesensors is located on the same platform/vehicle, for example pointed indifferent directions. Note also that, in some examples, one sensor on aparticular platform detects the signal, while another sensor on thatsame platform does not detect the signal (for example, because they donot point in the same direction).

There is further shown a system 140, referred to herein as a systemcenter. This may, for example, receive transmissions of data 150 fromone or more of the sensors 105, 110, 115. It may use this information toperform an application task. In the non-limiting example applicationelaborated herein, of geo-location, system center 140 may use the datatransmissions 150 received from some or all of the sensors to calculatethe geographic location of one or more of the emitters 120, 130. Thismay be done, for example, using known geo-location techniques, involvingdifferential parameters such as Time of Arrival (TOA), Doppler or phase,using known techniques. In this example, system center 140 may bereferred to as a geo-locating system center. Sensors 105, 110, 115 andsystem center 140 may comprise a radio-based geo-locating system.

In some example embodiments, system center 140 may be a ground station.In other embodiments, it may be located on, or associated with,platforms such as airborne vehicles, balloons, space-borne vehicles,ground systems, ground vehicles, and water-borne vehicles. Although inthe example of FIG. 1 one system center 140 is shown, in other casesthere may be multiple system centers 140. In some cases, the multiplesystem centers 140 may communicate with each other, and workcollaboratively, for example to calculate the location of the emitters120, 130.

The above discussion exemplifies a case where the sensors sendinformation to the system center 140, which is not a sensor, whichperforms an application task. In other example cases, however, thesensors could send the information to one (or more) of the sensors,which have sufficient processing power to calculate and perform theparticular application task. In that sense, the particular sensor(s) mayfunction as a system center as well. In other examples, the systemcenter may be associated with processing circuitry separate from that ofa sensor, but maybe physically co-located with the sensor. In oneexample, both systems may be located in the same truck.

FIG. 1 also shows inter-sensor communication 160. In some cases, thiscommunication will be of a narrower bandwidth, that is of a lower datarate, as compared to the bandwidth and data rate of data transmissions150 between sensors and system center 140. A use of suchnarrow-bandwidth inter-sensor communication 160 for the purpose ofassisting in signal detection is described herein.

It should be noted here, that when reference is made to sending ofinformation from one component to another, e.g. from one sensor toanother sensor, or from one sensor to the system center 140 or viceversa, the subject matter contemplates various methods for routing suchinformation. In some examples, the sending may be directly from onecomponent to another (e.g. 105 to 110). In other examples, the data maybe broadcast, such that numerous other components may receive it. Instill other examples, the source component may send to the destinationcomponent via a third component functioning as a relay for thetransmission. This may be done based on configuration of components, inorder to handle cases such as lack of Line of Sight (LOS) between thesource component and the destination component, at a time when bothsource and destination have LOS to the third component. For example, adetecting sensor 105 may send information to a non-detecting sensor 110via the system center 140. Another example may be a sensor 105 sendinginformation to the system center 140 via another sensor 115. Similarly,the system architecture 100 may additionally include one or more relays180. These may be any type of component that functions neither as asensor nor as a system center, but is configured to, and capable of,communicating with one or more sensors and/or one or more system centersso as to relay data between any or all of them as needed. Thiscommunication is shown in a generalized schematic fashion as 182. Onenon-limiting example of such a relay 180 may be a geo-stationarysatellite with LOS to at least two of the other components. It is alsoenvisioned, that a communication between components may in some cases berelayed via more than one relay 180 in order to reach its destination.

Turning now to FIG. 2A, it illustrates one example of electro-magnetictransmissions received at a sensor, in accordance with certainembodiments of the presently disclosed subject matter. FIG. 2A shows anexample representation, in the frequency domain, of receivedelectro-magnetic transmissions during a time interval T1, such as e.g. aprocessing frame of a signal processor 335 (described further hereinwith regard to FIG. 3). Note that in some cases a processing frame maybe considerably smaller than a dwell. In the example shown in FIGS. 1and 2, the transmissions were received by Sensor 1, 105. FIG. 2A shows agraph 205, plotting the magnitude of data 223 received at time T1,indicative of the entire electro-magnetic transmission, as a function offrequency. This magnitude may be referred to interchangeably herein alsoas power level or intensity. Electro-magnetic transmissions may be ofvarious frequencies. Frequency range 220 may be referred to as afrequency band 220, analyzed by sensor 105 so at to detect and estimateparameters of signals that were emitted in that range by one or moreemitters. Sensor 105 may receive and process all, or some, of the entiredata of such a frequency band 220. Note also that sensor 105 may becapable of, and configured for, scanning more than one frequency band220, scanning a frequency band during each dwell.

It can be seen in the figure that transmissions at different frequenciesmay be received at different power levels or magnitudes. For example, itcan be seen that the received transmission 222 at and around frequencyf₁ is of a higher magnitude than the received transmission 226 at andaround frequency f₃. The received transmissions 224 and 228, forfrequency f₂ and f₄, are at lower magnitudes than both 222 and 226 theothers, and are at levels near or below the detection level 217 for thissensor, that is their signal-to-noise ratio (SNR) is comparatively low.It may thus be said that received transmissions 222 and 226 containsignals emitted by emitters 120, 130, that are capable of being detectedby sensor 105, as they are sufficiently above the detection level 217 tobe detected and identified; that is, their signal-to-noise ratio (SNR)is comparatively high. It may also be said that received transmissions224 and 228 are not sufficiently above the detection level 217 to bedetected and identified, and thus that sensor 105 did not detect emittedsignals in the time T1 corresponding to frequency f₂ and f₄. Note thatone example reason for a detection level, below which a signal may notbe detected, may be noise.

It may be thus understood, that not every sensor in a selected sensorgroup will always detect all emitted signals that other sensors in thesensor group detect. For example, in FIG. 1 it may be that sensors 105and 115 may detect the particular signal emitted by emitter 130 at acertain point in time, while sensor 110 does not detect the same emittedsignal corresponding to the same point in time.

One example reason may be that sensor 110 is positioned in a directionrelative to the emitter 130, such that it receives transmissions fromside or back lobes rather than from the main lobe. See for example thearrangement in FIG. 1. Another example reason may be the greaterdistance of sensor 110 from emitter 130, which may cause the signal fromemitter 130 received at sensor 110 to be weaker than that received ate.g. sensors 105. In such cases, the signal from emitter 130 received atsensor 110 may be possibly sufficiently weak that the Signal to NoiseRatio (SNR) does not enable the emitted signal to be detected relativeto the noise received corresponding to the same frequency.

Note that that the depiction with regard to FIG. 2 is only onenon-limiting example. The figure presents a case where eachtransmission, and each signal emitted from a particular emitter, beingreceived at all of the sensors in the same time. In some examples, thismay be the case. In other examples, there may be lags in the time that aparticular signal reaches two different sensors. Such a delay may becaused, for example, by the different distances of each sensor from theemitter. Sensors in a selected sensor group may in some cases besynchronized with each other. In some examples, two sensors may know therelative delay between them in receiving the same signal. In someexample cases, this lag is not known a priori, but may be determinedduring the process of extracting signals. (One non-limiting example ofthis latter case may be seen with respect to the example Time of Arrivalcalculations presented with regard to FIG. 7A.) Therefore, in somecases, if a detecting sensor receives a signal during a defined timeinterval, the non-detecting sensor may perform an action with respect todata received in a different time interval, a related time interval thathas a correspondence to the defined time interval, but that isdelay-adjusted or offset from the defined time interval by the amount ofthe lag. Such a related defined time interval may be referred to hereinas a corresponding defined time interval. As already indicated, in somecases the corresponding defined time interval may be equal to thedefined time interval during which the detecting sensor receives thesignal.

It should also be noted, that FIG. 2 show only a non-limiting example ofa single detection level 217 for all the sensors. In some example cases,the detection level may vary per sensor, based on for example noiseconsiderations. Thus, detection and non-detection of a particular signalby a particular sensor may be a function of the detection level of thatsensor. For example, consider a case where two sensors both receive asignal at an magnitude of 10. The first sensor has a detection level of2, while the second sensor has a detection level of 11. In such a case,the first sensor may detect, while the second does not detect—despitethe fact that each received the signal at the same magnitude.

Note that in some cases, the frequencies f₁, f₂, f₃ and f₄ may befrequency bins. Frequency bins are discussed further herein.

Further elaboration of FIGS. 2A-2F is presented further herein.

In some example implementations known in the art, sensors may transmitdata 150 to system center 140 using the following mechanism. Sensorsthat detect a signal may send data corresponding to each detected signaland descriptive of the detected signal. In some implementations, thisdata may be a set of parameters. One example of such a set of parametersis a Pulse Parameters Set. The Pulse Parameters Set may contain at leastthe following fields: time of arrival, signal frequency, magnitude orstrength of the detected signal, or possibly SNR (Signal to NoiseRatio), and pulse width. In the example of FIG. 2A, for one of thedetected signals, the pulse parameters set may correspond to T1,frequency f₁ and magnitude of 222, which is represented by the examplevalue “10”. System center 140 receives the transmissions 150 fromsensors of the selected sensor group that detected signals. Sensors thatdid not detect a signal during T1 may send no data corresponding to thatsignal. If a sufficient number of sensors in the group report, in theirtransmission, that they detected a particular signal during a particulartime interval, e.g. a signal of frequency f₁ during T1, the systemcenter 140 may be able to make use of this information to perform anapplication task. For example, for the application of geo-location, thesystem center may be able to use known methods to determine the locationof the emitter (e.g. 120) that emitted that signal during that timeinterval. If on the other hand, an insufficient number of sensors in thegroup report in their transmission that they detected a particularsignal during a particular time interval, system center 140 may haveinsufficient information to be able to perform an application task. Forexample, the system center may be unable to geo-locate that emitterduring that time interval. The location attempt for that time intervalmay thus be unsuccessful.

Turning to FIG. 3, there is now provided a description of certainexamples of systems for signal detection.

Reference is now made to FIG. 3A, which is a block diagram schematicallyillustrating an example sensor, in accordance with certain embodimentsof the presently disclosed subject matter. In some examples, sensor 305may include at least one receiver 315, in addition to other components.

The receiver 315 may in some examples include a computer. It may, by wayof non-limiting example, comprise processing circuitry 350. Processingcircuitry 350 may comprise a processor 320 and memory 325.

The processor 320 is shown, in the particular example of FIG. 3A, ascomprising two component processors: receiver processor 342 andcontroller processor 374. Receiver processor 342 in turn is shown ascomprising three component processors: sampler 330, signal processor335, detecting and identifying processor 340. Examples of the functionsof these various component processors will be further elaborated withregard to FIG. 3B.

The processing circuitry 350 may also include, in some examples, one ormore memories 325. According to some examples of the presently disclosedsubject matter, the memory 325 can be configured to hold configurationdata of the sensor (e.g. what sensors are part of each selected sensorgroup), emitter data (used e.g. for identifying detected emitters).Memory 325 can also be used, for example, to hold at least some dataassociated with calculations and determining described herein fordetecting signals. These are non-limiting examples of data items thatmay make use of memory 325. The memory 325 is shown, in the particularexample of FIG. 3A, as comprising two component memories: receivermemory 346 and controller memory 376.

Considering the processors and memories from a functionality point ofview, receiver processor 342 and receiver memory 346 may in someexamples be viewed as comprising a receiver functionality 315. 315 isshown in broken lines, to indicate that it is a functionality. Receivermemory 346 may provide the memory used by receiver processor 342 and, insome examples, by the three component processors 330, 335, 340. Thesecomponents may work together, functionally, to receive and processsignals from the receiver antennas, as will be further elaborated withregard to FIG. 3B and elsewhere herein.

Similarly, considering the processors and memories from a functionalitypoint of view, controller processor 374 and controller memory 376 may insome examples be viewed as comprising a controller functionality 370.370 is shown in broken lines, to indicate that it is a functionality.Controller memory 346 may provide the memory used by controllerprocessor 342. Examples of functions that may be viewed, in some cases,as those of a controller functionality 370 will be further elaboratedwith regard to FIG. 3B and elsewhere herein.

There may be, in some cases, multiple instances of the controllerfunctionality 370. In example cases, some instances of the controllerfunctionality may include a processor and a memory, and some may bebased purely on electrical circuits with electrical inputs, without amemory.

The processing circuitry 350 may be, in non-limiting examples,general-purpose computers specially configured for the desired purposeby a computer program stored in a non-transitory computer-readablestorage medium. They may be configured to execute several functionalmodules in accordance with computer-readable instructions. In othernon-limiting examples, processing circuitry 350 may be computersspecially constructed for the desired purposes.

The sensor 305 may also include, in some examples, receiver antennas310. These may be operatively coupled or connected to the receiver 315.Examples of receiver antennas functions will be further elaborated withregard to FIG. 3B.

The sensor 305 may also include, in some examples, data links 313. Thesemay be operatively coupled or connected to the receiver 315. These mayinclude system center data link 317 and sensor data link 319. Examplesof data link functions will be further elaborated with regard to FIG.3B.

The sensor 305 may also include, in some examples, storage 360. Storage360 may include, as non-limiting examples, the recorders 363 and 365which are described with regard to FIG. 3B. Depending on system design,more or less of the data storage may occur in memory 325 or in storage360.

Reference is now made to FIG. 3B, which is a block diagram schematicallyillustrating an example sensor, in accordance with certain examples ofthe presently disclosed subject matter. For purposes of clarity ofexposition, the information exemplified in FIGS. 3A and 3B has beenseparated into two figures. FIG. 3A describes, at a high level, examplecomponents of the system. FIG. 3B describes possible exampleinteractions between certain of those example components and/or certainof their sub-components. Thus, in the example shown in FIG. 3B,processing circuitry 350, processor 320 and its components 342 and 374,and memory 325 and its components 346 and 376, are not shown. Similarly,the sub-components of controller functionality 370 are not shown.Similarly, recorders 363 and 365 are shown, but not storage 360.Similarly, system center data link 317 and sensor data link 319 areshown, but not data links 313. This is all done for clarity ofexposition.

Receiver antennas 310 of sensor 305 may receive electro-magnetictransmissions, which may include both signals from emitters as well asnoise. It may scan the frequencies in a synchronized fashion. Allsensors in a selected sensor group may be synchronized, such that allscan the same frequency band 220 during the same dwell N. Thefunctionality of controller 370 may include controlling the process,e.g. instructing receiver antennas which band to scan in a particulardwell. The band to be scanned may also change during the process, forexample based on updates received by processor 374 of the controller 370from the system center 140. In some cases, instead of scanningsequentially through the frequencies, the entire frequency band can bereceived at once.

Sampler 330 may be operatively coupled or connected to Receiver antennas310. Sampler may receive data associated with the scanned frequency band220 that was received during a particular dwell number. The sampler mayperform analog to digital conversion on certain frequency bands perdwell. This sampling may be performed at a sampling rate f_(s). Theoutput of this may be samples. In example cases, these samples maycomprise amplitude and phase information for each sampling time.

Signal Processor 335 may be operatively coupled or connected to Sampler330. Signal processor 335 may process those received samples, by forexample performing digital filtering on them, thus deriving processedsamples in the frequency domain. It may use, for example, FFT (FastFourier Transform) or some other filtering technique. This may yieldfrequency bins, also referred to herein interchangeably as bins, eachwith amplitude and phase information.

Detecting and Identifying Processor 340 may be operatively coupled orconnected to Signal Processor 335. It may determine in what bins itdetects signals. It may, in some example cases, analyze individualpulses and determine which represent a particular signal. In someexample cases, it may cross-correlate data in its own bin with data thatit received from other sensors. In some cases, it may perform parameterestimation, for example determining Pulse Parameter Set values. In somecases, it may calculate difference data, involving differentialparameters such as TOA, Doppler or phase, based on data of two sensors.The term Detecting and Identifying Processor is used here forconvenience, but does not limit the functions that processor 340 mayperform.

The processors 330, 335 and/or 340 may make use of receiver memory 346(shown in FIG. 3A but not in 3B), comprised in memory 325, to store datawhile performing analysis and calculations, among other uses.

Data links 313 (shown in FIG. 3A but not in 3B) may include, in additionto other components, system center data link 317 and sensor data link319. These may interface to, respectively, system center 140 and sensors105, 110, 115, for example. They may be configured to route datadirectly to its destination, or via a relay or other components, aselaborated with regard to FIG. 1. The interface may be realized by anysignaling system or communication components, modules, protocols,software languages and drive signals, and can be wired and/or wirelessas appropriate.

Detecting and Identifying Processor 340 may be operatively coupled orconnected to Recorder #2 365, which in turn may be operatively coupledor connected to system center data link 317. When Processor 340 succeedsin detecting a signal, or has data indicative of a detected signal, itmay send it via the system center data link 317. Recorder #2 365 is abuffer which may store data to be sent, before it is sent over data link317. This buffering may occur, for example, because system center datalink 317 does not have LOS to system center 140, and thus cannotcommunicate the data immediately. The buffering may also occur, forexample, due to the large amount of data to be communicated to 140.

Detecting and Identifying Processor 340 may also be operatively coupledor connected to sensor data link 319. This may enable communication ofdata between sensors, for example from a detecting sensor to anon-detecting sensor. A buffer or recorder (not shown) may in some casesexist also for this communication. It is not shown, to exemplify thepossibility of the traffic on this data link requiring a lower data rateas compared to traffic over system center data link 317, which mayrequire a higher data rate. Data link 319 may have a lower bandwidthcapacity, due to for example capacity constraints in the sensor ascompared to system center 140, which in some cases may be a largerand/or higher-capacity device.

Recorder #1 363 may be operatively coupled or connected to at leastSampler 330, Signal Processor 335, and Detecting and IdentifyingProcessor 340. For example, 330 and 335 may write samples, and processedsamples, respectively, to Recorder #1 363. Processor 340 may accessrecorder 363, for example, in order to process data stored in 363. Itshould be noted that other, shorter-term buffers, used for exampleduring signal processing, may exist but are not shown.

Controller functionality 370 may be operatively coupled or connected tosome or all the other components and sub-components in the sensor. Thisinterface 373 is therefore shown in a schematic fashion, as a brokenline. The individual connections are not depicted, for clarity of thedrawing. The functionality 370 may monitor and control all of theprocesses. Non-limiting example functions that it may perform include:synchronizing; determining whether LOS to 114, 105, 110, 115 exist andthus the data links 317, 319 may communicate when data should be savedto, and accessed from, recorders 363, 365. Similarly, controllerfunctionality 370 may be involved in data reduction, instructing forexample processor 340 to save, process and send only a portion of thedata received during a defined time interval. In some examples, incomingassistance information sent by a detecting sensor may be sent to thecontroller, which decides what to do with it, and how it should be usedfor assisted detection in the non-detecting sensor. Some or all of thesefunctions may be performed by controller processor 374, comprised inprocessor 320. Non-limiting example data to be stored in controllermemory 376, which is comprised in memory 325, may include the bands tobe scanned per dwell.

Examples of the above interactions are described further herein withregard to other figures.

FIGS. 3a and 3b illustrate only a general schematic of the systemarchitecture, describing, by way of non-limiting example, one aspect ofthe presently disclosed subject matter in an informative manner only,for clarity of explanation only. Only certain components are shown, asneeded to exemplify the presently disclosed subject matter. Othercomponents and sub-components, not shown, may exist. For example, insome cases, some components may be implemented as analog devices such asfilters, instead of as processors. For example, Sampler 330 and/orSignal Processor 335 may in some cases be fully or partly replaced byanalog filters. Systems such as those described with respect to thenon-limiting examples of FIG. 3, may be capable of performing all, some,or parts of the methods disclosed herein.

It will be understood that that the teachings of the presently disclosedsubject matter are not bound by what is described with reference toFIGS. 3a and 3 b.

Each system component in FIG. 3 can be made up of any combination ofsoftware, hardware and/or firmware, executed on a suitable device ordevices, that perform the functions as defined and explained herein.Equivalent and/or modified functionality, as described with respect toeach system component, can be consolidated or divided in another manner.Thus, in some examples of the presently disclosed subject matter, thesystem may include fewer, more, modified and/or different components,modules and functions than those shown in FIG. 3. To provide onenon-limiting example of this, in some examples the functions of thesub-processors 330, 335 and 340 may be combined into processor 320. Oneor more of these components can be centralized in one location ordispersed and distributed over more than one location.

Each component in FIG. 3 may represent a plurality of the particularcomponent, possibly in a distributed architecture, which are adapted toindependently and/or cooperatively operate to process various data andelectrical inputs, and for enabling operations related to signaldetection. In some cases multiple instances of a component, may beutilized for reasons of performance, redundancy and/or availability.Similarly, in some cases, multiple instances of a component may beutilized for reasons of functionality or application. For example,different portions of the particular functionality may be placed indifferent instances of the component.

The communication between the various components of sensor 305, in caseswhere it is not located entirely in one location or in one physicalcomponent, can be realized by any signaling system or communicationcomponents, modules, protocols, software languages and drive signals,and can be wired and/or wireless as appropriate.

Turning to FIG. 4A, there is illustrated one example of a generalizedflow chart diagram of providing assistance information between sensors,in accordance with certain embodiments of the presently disclosedsubject matter. In some embodiments, one or more steps of FIG. 4A may beperformed automatically. The flow and functions illustrated in FIG. 4Amay for example be implemented in processing circuitry 350, and may makeuse of components and sub-components described with regard to FIGS. 3Aand 3B.

The example flow 400 starts at 405. In step 405, the receiver antennas310 of sensor 105 may receive electro-magnetic transmissions, and mayscan the frequencies in a synchronized fashion. All sensors in aselected sensor group may be synchronized, such that all scan the samefrequency band 220 during the same dwell N. Controller 370 may controlthe process, e.g. instructing receiver antennas which band to scan in aparticular dwell. The band to be scanned may also change during theprocess, for example based on updates received by the controller 370from the system center 140.

In step 410, the sampler 330 may sample data associated with the scannedfrequency band 220 that was received during a particular dwell number,shown in the figure as dwell N. Dwell N is an example of a defined timeinterval during which data indicative of the entire data of a frequencyband is received by the sensor. Note that the dwells of all sensors maybe synchronized, although their start and end times may in some casesnot coincide.

This data sample may in some cases comprise the entire data of afrequency band received by the sensor during the defined interval. Inother cases it may comprise only a portion of the frequency band. Inexample cases, these samples may comprise amplitude and phaseinformation for each sampling time.

In step 415, the sampler may then record this sample data, in, forexample, the first recorder 363, for possible future use.

Possibly in parallel with step 415, but not necessarily so, in step 411the signal processor 335 may process those received samples, by forexample filtering them to the frequency domain, thus deriving processedsamples. It may use, for example, FFT (Fast Fourier Transform) or someother filtering technique.

In step 417, the signal process may then record this sample data in, forexample, the first recorder 363, for possible future use.

Possibly in parallel with step 417, but not necessarily so, in step 412the detecting and identifying processor 340 may analyze those processedsamples that correspond to a first frequency of interest X. This may befor example the frequency bin that corresponds to 222 or 224 in FIG. 2.The analysis may include determining whether data of a sufficientstrength above the expected detection level 217 has been received, whichwould indicate or enable detection of an emitted signal in the frequencybin. It is assumed, in the examples, that only one signal is associatedwith a bin. In step 420, detecting and identifying processor 340 makes adetermination whether a signal emitted by an emitter 120 has beendetected corresponding to that frequency bin. That is, it may determinewhether the data indicative of the entire data of the frequency bandincludes a signal emitted by an emitter in the frequency bin. Note thatthe example discussion with regard to these figures is with respect tofrequency bins. However, in some cases, e.g. where an analog filter isused, the signals may correspond to a frequency rather than to afrequency bin. Note that it may also be important, that all sensors thatcommunicate frequency-associated information between them are aware ofthe format that the information is sent—that is whether frequencies areexpressed in terms of a frequency or a frequency bin.

Note that the depiction with regard to FIG. 2 is only a non-limitingexample, to illustrate for example that at different points in timedifferent sensors may detect different signals. The example depictionindicated that the emitter frequency fell into one frequency bin.However, in other cases, the emitter frequency may fall, for example,into two frequency bins. Similarly, the example depiction was that ateach time interval T1, T2 detection occurred at particular sensors.However, as will be seen further herein with reference to FIG. 9A, forexample, in some cases, a signal pulse may last for more than oneprocessing frame, and thus several intervals T1, T2 etc. may pass untildetection of a signal pulse is made.

In response to the determination at step 420 being Yes, that thecriterion was met, indicated by flow arrow 422, the sensor may beconsidered a detecting sensor, with respect to the particular frequencybin X and dwell N. For example, in graph 205 of FIG. 2A it may be saidthat sensor 105 detected signal 222 of the frequency f₁ during a definedtime interval, for example dwell N, and is a detecting sensor.

In step 421, the detecting and identifying processor 340 may sendassistance information, corresponding to the signal emitted by theemitter which sensor 105 detected, to one or more other sensors. Thesesensors should include at least one non-detecting sensor in the selectedsensor group, that is one sensor that did not detect a signal in thatparticular frequency bin and dwell N, as will be discussed furtherherein. The information may be sent to all sensors in the group, e.g.via broadcast, or only to those sensors that did not detect the signal.Example cases further herein describe examples of such communication.The assistance information may be sent via sensor data link 319.

In some example cases, the assistance information may not include theentire data that corresponds to the frequency band 220, which wasreceived by the detecting sensor during the defined interval (e.g. dwellN)—which includes a comparatively large amount of data—but rather mayinclude a smaller amount of data. Non-limiting examples of assistanceinformation are described further herein.

In optional step 430, detecting sensor 105 may, in some example cases,send data indicative of the detected emitted signal 222 to anothersystem, for example to system center 140. This data may be sent via datalink 317, and may be buffered for some time in second buffer 365. Notethat step 430 may occur before step 421, or in parallel, in certainexamples.

At step 452, detecting and identifying processor 340 may determinewhether all frequency bins of interest (or, in some cases, frequenciesof interest) in the scanned frequency band have been analyzed. In someexamples, the list of frequency bins of interest may be stored instorage 360, and may be updated by the controller functionality 370(e.g. making use of controller processor 374 and controller memory 376).

In response to the determination at step 452 being No, that thecriterion was not met, indicated by flow arrow 454, the flow maycontinue to 456, analysis of samples for the next frequency or frequencybin. The flow then proceeds to “A” (460, 462), looping back to step 420,for determination whether an emitted signal was detected at this nextfrequency or frequency bin.

In response to the determination at step 452 being Yes, that thecriterion was met, indicated by flow arrow 457, the flow may continue tostep 460. In 460, the receiver 315, perhaps using the sampler 330,increases the dwell number N by 1, and then loops back to step 410, inwhich it samples data received during the new dwell N.

Returning to the decision point in step 420, in response to thedetermination at step 420 being No, that the criterion was not met,indicated by flow arrow 424, the sensor may be considered anon-detecting sensor, with respect to the frequency bin X and dwell N.For example, in graph 209 of FIG. 2C, depicting electro-magnetictransmission data received at sensor 110, it may be seen that sensor 110did not detect a signal within the received data 240 corresponding tofrequency f₁ during the dwell N, since received data 240 is at levelsnear or below the detection level 217 for this sensor. Continuing tostep 440, the detecting and identifying processor 340 of non-detectingsensor 110 may take no action regarding frequency bin X and dwell N, andmay wait regarding such action, until it receives a transmission ofassistance information from other sensors, possibly sensors in the samegroup. In some examples, if no assistance information is sent within aconfigured time interval, sensor 110 may delete or discard the relevantdata that it buffered in steps 415 and/or 417.

In step 441, detecting and identifying processor 340 of non-detectingsensor 110 may receive such a transmission, from at least one detectingsensor, containing assistance information corresponding to an emittedsignal detected by the detecting sensor, which in turn corresponds tothe same dwell N. This may be, for example, the transmission ofassistance information that was done by detecting sensor 105 in step421. This information may arrive, for example via sensor data links 319.

In step 446, detecting and identifying processor 340 of non-detectingsensor 110 may now have a more enriched set of information regarding thedata sample it received in the frequency bin X and dwell N, because theassistance information provided by detecting sensor 105 providedsupplemental information that non-detecting sensor 110 did notpreviously have. Utilizing this provided assistance information,detecting and identifying processor 340 of non-detecting sensor 110 mayperform an action with respect to data indicative of the entire data ofthe frequency band received by sensor 110 during the correspondingdefined time interval (e.g. corresponding to dwell N). The actions maycorrespond to the emitted signal which was received by the at least onenon-detecting sensor during the corresponding defined timeinterval—although sensor 110 has not detected this signal. Non-limitingexamples of actions that may be performed are described further herein.In some examples of such actions, it may be said that the non-detectingsensor used the assistance information to perform an assisted detection.

In some example cases, the action performed in step 446 with respect todata indicative of the entire data of the frequency band, received bythe non-detecting sensor during the corresponding defined time interval,may be utilized for perform an application task such as determining thelocation of the relevant emitter 120 at the defined time intervalcorresponding to these data. In some example cases, this applicationtask may be performed by system center 140.

It should also be noted, as already elaborated with regard to FIG. 1,that sending of the information in steps 421 and 430 may be done, forexample, directly, via other sensors, via the system center, via arelay.

In steps 452, 454, 456, 461, 462, and 457, 460, detecting andidentifying processor 340 of non-detecting sensor 110 may determinewhether all frequencies or frequency bins in the scanned frequency bandhave been analyzed, and may act accordingly, in a manner detailed hereinregarding detecting sensor 105.

It should be noted that the loop shown is for ease of exposition only,to more easily explain concepts. In some examples, steps such as 420,422, 421, 430, 440, 441, 446, 452, 454, 456, 460, 462 may be performedsimultaneously for multiple frequencies or frequency bins. This appliesas well to other figures herein that show a similar looping overfrequencies or frequency bins. Similarly, in some example cases, thesesteps may be performed simultaneously for multiple dwells. It may not benecessary to perform these steps only for one dwell at a time.

Before turning to example implementations of the above flow 400, somepossible advantages of providing assistance information from a detectingsensor to a non-detecting sensor, in accordance with certain exampleembodiments of the presently disclosed subject matter, will bementioned. Thus, in some system architectures 100 of signal detectionknown in the art, it may be the case that when an insufficient number ofsensors in the selected sensor group report in their transmission thatthey detected a particular signal during a particular time interval,system center 140 may have insufficient information available to be ableto perform an application task, such as for example a geo-locationattempt, as elaborated above. In some cases providing the applicationmay be considered to work on an “all or nothing” basis, in that anopportunity to perform the task would have been missed, the resources ofthe system may have been wasted, for example the particular locationattempt would fail, even though one or more of the sensors hadsuccessfully detected the particular signal, and were able to providethat information to the system center—because one sensor did not detect.The inefficiencies of such a system are evident.

On the other hand, a system architecture 100 that makes use of a methodsuch as shown, for example, in FIG. 4A, may in some cases be able toperform the application task even in cases where an insufficient numberof sensors detected a particular signal. This may be achievable becausethe non-detecting sensor receives the assistance information from one ormore detecting sensors, and is able to use this supplementaryinformation to perform an action that may result in the system 100performing successfully the required task, such as for example locatingthe particular emitter during to the particular defined time interval.It may be said, in some examples, that the system 100, or in someexamples the non-detecting sensor 110, performed assisted detection. Thesystem sensitivity may be said to be improved, in that the system as awhole detects the signal and performs the associated task, even wherethe signal strength and the configuration of system 100 in that timeinterval is such that one or more sensors were not able to detect it.Similarly, the performance of the task may be achievable in a higherpercentage of cases. Also, in some cases, as will be seen e.g. regardingFIGS. 4B, 4C, 7A, only a portion of the received samples, or onlycertain parameters and calculated results, need be sent to system center140. In some cases this will enable simplified designs of sensors, sincesuch sensors will not require high-bandwidth communications systems inorder to send such data to e.g. system center 140.

It may thus be said that the performance of such a system may beimproved, and the utilization of the resources involved (e.g. sensorsand system centers) may be more efficient, over a similar system thatdid not make use of a method such as shown, for example, in FIG. 4A.

Additional example advantages may be presented herein, in the context ofparticular example implementations of the method of FIG. 4A.

Turning to FIG. 4B, there is illustrated one example of a generalizedflow chart diagram of providing assistance information between sensors,in accordance with certain embodiments of the presently disclosedsubject matter. The method described with regard to FIG. 4B may in someexamples be a specific implementation of the more general methoddescribed with regard to FIG. 4A. As such, much of the flow chart may besimilar, and elaboration will be made mainly of the steps that may notbe similar or identical.

The example flow 402 starts at 405. Steps 405, 410, 411, 415, 412, 417and 420 may be similar to that described with regard to FIG. 4A. Inresponse to the determination at step 420 being Yes, that the criterionwas met, indicated by flow arrow 422, flow proceeds to 423. In step 423the detecting and identifying processor 340 of the detecting sensor 105may extract, from the data indicative of the entire received data of thefrequency band, relevant data corresponding to the defined timeinterval, e.g. dwell N. This relevant data may include data indicativeof the emitted signal during the defined interval. In some examplecases, this may be data indicative of the entire data sample received bysensor 105 during the defined interval, that corresponds to the detectedemitted signal. For example, this may be data indicative of the entirereceived data sample, that correspond to times in which the signal wasdetected, and the times of those samples. The times of such samples maybe referred to as detection times of the at least one detected emittedsignal, where the start and end times of each detection may be referredto as defining or bounding a detection time interval. These may be, forexample, samples created by sampler 330. In some example cases, thisdata may be data indicative of the entire received data sample,corresponding to the frequency bin of the detected signal during thedefined time interval. These may be, for example, processed samples 222created by signal processor 335.

In step 426, the detecting and identifying processor 340 of thedetecting sensor may send to one or more other sensors assistanceinformation, which may include one or more instructions. Theinstructions may tell those other sensors that did not detect theparticular signal to save relevant data that is in the non-detectingsensors' recorder 363 corresponding to the defined time interval. Thisrelevant data may be data received by the non-detecting sensor duringthe defined time interval. This data may be data indicative of theentire data sample received by sensor 105 during the defined interval,that corresponds to the emitted signal detected by the detecting sensor105 during the defined time interval.

In some example cases, such relevant data may be data indicative of theentire received data sample, corresponding to the frequency bin of thedetected signal during the defined time interval. This may includeprocessed samples indicative of the frequency bin 222 corresponding tosample detection at the detecting sensor.

For example, such relevant data may be data indicative of the entirereceived data sample, that correspond to times in which the signal wasdetected, and the times of those samples. For example, the instructionmay include times during which the detecting sensor detected samples,and may instruct the non-detecting sensor to save samples for the sametimes. In some example cases, the method may account for different timesof arrival of the same emitted signal at different sensors. In such acase, the instruction may additionally be that the non-detecting sensorsaves samples from a certain time interval before, and a certain timeinterval (the same or different) after, those times corresponding tosample detection at the detecting sensor. Such time intervals would bedetermined as part of the engineering of the particular system andapplication, and would be configured appropriately. This may be oneexample of data reduction achievable using the methods of the presentlydisclosed subject matter. In other example cases, the detecting andidentifying processor 340 of the detecting sensor 105 would instruct tosave all samples or data corresponding to dwell N.

The sensors to receive this instruction information may include at leastone non-detecting sensor in the group. This assistance information maybe sent via a data link 319. Note that in some example cases, theassistance information will comprise a smaller amount of data, comparedto the entire data 223 that corresponds to the frequency band 220.

In optional step 432, the detecting and identifying processor 340 ofdetecting sensor 105 may, in some example cases, send data indicative ofthe detected signal 222 to another system, for example system center140. In some example cases, the data sent may be the pulse parametersset of the detected signal. In other example cases, 105 may send all ormost of the entire received data sample 223 of a frequency band, of theparticular frequency 222 or frequency bin 222 and dwell N for which thesignal was detected by 105. In some examples, 105 may send samples fortimes indicative of those times corresponding to sample detection at thedetecting sensor 105. Note that step 432 may occur before step 426, orin parallel, in certain examples.

In steps 452, 454, 456, 461, 462, and 457, 460, the detecting andidentifying processor 340 of detecting sensor 105 may determine whetherall frequency bins in the scanned frequency band have been analyzed, andact accordingly, in a manner detailed herein regarding FIG. 4A.

Returning to the decision point in step 420, in response to thedetermination at step 420 being No, that the criterion was not met,indicated by flow arrow 424, in step 440, the detecting and identifyingprocessor 340 of non-detecting sensor 110 may take no action regardingthe frequency bin and dwell N, and may wait regarding such action, untilit receives a transmission of signal-related data from other sensors,possibly sensors in the same group. In step 443, the detecting andidentifying processor 340 of non-detecting sensor 115 may receive such atransmission, from at least one detecting sensor, containing theassistance information, corresponding to a signal detected by thedetecting sensor. This may include the instruction, sent by detectingsensor 105 in step 421, to save data indicative of the signal detectedat the detecting sensor 105. The instructions may be received via datalink 319, and possibly controller processor 374.

In step 447, non-detecting sensor 110 may use this assistanceinformation to save the relevant data, that is data indicative of thesignal detected at the detecting sensor. Examples of such data aredescribed with respect to step 426. Policies configured in sensor 110may cause it to save the data if at least one detecting sensorinstructed it to do so.

Rather than discarding the samples, possibly because they did notindicate detection of a signal, the particular buffer data is, in such acase, saved for at least some amount of time. The data is thus not lost.This buffered data in some example cases may continue to be saved inrecorder 363. In other example, cases, this buffered data may be savedelsewhere in storage 360. In some example cases, the time interval forwhich the buffered data will be saved is configured in the non-detectingsensor. In other example cases, the detecting sensor may have instructedthe non-detecting sensor for how long this buffered data should besaved.

In step 450, the non-detecting sensor, e.g. using the detecting andidentifying processor 340, may also optionally send to the system center140 data indicative of the saved sample. For example, it may send atleast a portion of the saved data to a system center when communicationto the system center is available. In some cases it may send the entiresaved data.

In other examples, sensor 110, e.g. using the detecting and identifyingprocessor 340, may save this sample data for a longer time period, andmay asynchronously send at a later time this same data, or datacorresponding to it, at a later time. This might be done, for example,in a case where LOS is not available at that moment between sensor 110and system center 140, and thus communication to the system center isavailable.

In some cases, performance of the steps 426, 447 and/or 450 may beconfigured in the system 100, due to CPU (central processing unit) orother processing capacity limitations that may prevent non-detectingsensor 110 from performing more complex calculations on the data 223,such as those shown with regard to other example cases described herein.The system center may be capable of utilizing the data sent bynon-detecting sensors 110 in step 450, in real time or at a later time,possibly together with data sent by detecting sensors in step 432, toperform an application task such as determining the location of therelevant emitter 120 at the defined time interval corresponding to thesedata. Thus, in some cases the application task is performed despite thefact that an insufficient number of sensors detected the correspondingsignal.

In steps 452, 454, 456, 461, 462, and 457, 460, non-detecting sensor 110may determine whether all frequency bins in the scanned frequency bandhave been analyzed, and act accordingly, in a manner detailed hereinregarding FIG. 4A.

The method of FIG. 4B may provide, in some cases, certain additionaladvantages. In some cases, the non-detecting sensor 110 may save andbuffer only the data it was instructed to save in step 426, until it isable to send the data to e.g. system center 140. As discussed withrespect to step 426, the data to be saved may, in some cases, be lessthan the entire data received at non-detecting sensor 110. In some casesthis will enable simplified designs of sensors, since such sensors willnot require a large buffer storage capacity in order to save such datauntil they are able to communicate with e.g. system center 140. This maybe one example of data reduction achievable using the methods of thepresently disclosed subject matter.

Turning to FIG. 4C, there is illustrated one example of a generalizedflow chart diagram of providing assistance information between sensors,in accordance with certain embodiments of the presently disclosedsubject matter. The method described with regard to FIG. 4C may be, insome examples, a specific implementation of the more general methoddescribed with regard to FIG. 4A. As such, much of the flow chart may besimilar, and elaboration will be made mainly of the steps that may notbe identical.

The example flow 404 starts at 405. Steps 405, 410, 411, 415, 412, 417and 420 may be similar to that described with regard to FIG. 4A. Inresponse to the determination at step 420 being Yes, that the criterionwas met, indicated by flow arrow 422, in step 423 the detecting andidentifying processor 340 of the detecting sensor 105 may extract, fromthe data, relevant data. This may be data 223 indicative of the entirereceived data of a frequency band of interest. In some cases this may bedata indicative of that portion 222 of the entire received signal thatcorresponds to the frequency band received by the detecting sensorduring the defined time interval, which includes the detected signal. Insome example cases, such relevant data may include processed samples 222indicative of the frequency f₁ corresponding to sample detection at thedetecting sensor. In some example cases, such relevant data may includesamples for times indicative of those times corresponding to sampledetection at the detecting sensor.

In step 425, the detecting and identifying processor 340 of theprocessor 320 of the detecting sensor may send, to one or more othersensors, assistance information. This information may in some casesinclude data indicative of the entire received data at detecting sensor105 corresponding to the emitted signal 143 detected at sensor 105. Thismay be, for example, all of the data extracted in step 423, or someportion of that data. In some examples, this data indicative of theentire received data at detecting sensor may also include parametersassociated with the data. On example of this is sending informationabout frequency bin(s), in a case where the sent data includes samplesindicative of the frequency bins(s) corresponding to sample detection atthe detecting sensor. In some example cases, sensor 105 may sendassistance information to sensors that did not detect the particularemitted signal, as well as possibly to sensors that did detect theparticular emitted signal.

It should be noted here, with reference to FIG. 2A, that data indicativeof the entire received, such as for example data 222, is of a narrowerbandwidth than data 223 corresponding to the entire frequency band 220.In some cases the data of a frequency bin corresponding to a signalcomprises about 10%, or even less, of the data of the entire frequencyband 220. In some cases the duty cycle of the emitter pulses may be 10%of the time. Thus, samples corresponding only to times of signal pulsesmay comprise in such cases 10% of the total data sample received. Ifsensor 105 is configured to send data filtered only on signal times, oronly on a frequency bin, it may thus send in some cases data reduced to10% or less of the received data sample. If the sensor is configured tofilter on both frequency bin and signal time, it may send in some casesdata reduced to 1% or less of the received data sample. In some examplesit may send in some cases data reduced to about 0.1% or less of thereceived data sample. In some examples it may send in some cases datareduced to about 0.05% or less of the received data sample. Theinter-sensor communication interface 160 may thus be considered torequire a relatively narrow bandwidth, as compared to communicationinterfaces which must carry the entire data sample 223. This may be oneexample of data reduction achievable using the methods of the presentlydisclosed subject matter.

In step 433, the detecting and identifying processor 340 of theprocessor 320 of the detecting sensor 105 may send data relevant to theparticular application to another system, e.g. system center 140, forfurther processing. This relevant data may be, for example, all of thedata extracted in step 423, or some portion of that data. In some cases,the detecting and identifying processor 340 may determine a set ofparameters to send. This may be for example the pulse parameters set forthe detected signal, based on the data indicative of the entire receivedsignal 222 that corresponds to the particular frequency f₁ for which thesignal was detected and dwell N. Also, in example cases where detectingsensor 105 sends also to other detecting sensors, and possibly thosesensors send to it, sensor 105 can calculate also difference data, asdescribed further herein with respect to 448, and it can send thedifference data as well in step 433. This may even occur if all sensorsin a group detected a particular signal. Note also that step 433 mayoccur before step 425, or in parallel, in certain examples.

In steps 452, 454, 456, 461, 462, and 457, 460, detecting sensor 105 maydetermine whether all whether all frequency bins in the scannedfrequency band have been analyzed, and act accordingly, in a mannerdetailed herein regarding FIG. 4A.

Returning to the decision point in step 420, in response to thedetermination at step 420 being No, that the criterion was not met,indicated by flow arrow 424, in step 440, the detecting and identifyingprocessor 340 of non-detecting sensor 110 may take no action regardingthe frequency bin and dwell N, and may wait regarding such action, untilit receives a transmission of signal-related data from other sensors,possibly sensors in the same group. Waiting is one non-limiting exampleimplementation of the method of step 440, and of step 740, in all of therelevant Figures. In other examples, non-detecting sensor 110 mayrequest other sensors in the selected sensor group to provide assistanceinformation. In other examples, non-detecting sensor 110 may wait for acertain configured time, and, after timeout, it may request othersensors in the selected sensor group to provide assistance information.

In step 442, non-detecting sensor 110 may receive such a transmission,from at least one detecting sensor, containing assistance information,containing relevant data corresponding to a signal detected by thedetecting sensor. This may include the data indicative of the entirereceived data sample at the detecting sensors corresponding to thedetected emitted signal 143, and any relevant accompanying parameters,which was sent by detecting sensor 105, and possibly others, in step425.

The next step, 444, may be trivial, if only one detecting sensor 105sent data in 425 that was received in 442. In such a case, the basis forthe steps following 444 is the data sent from 105. However, it ispossible that more than one detecting sensor, e.g. both 105 and 115, maysend data in their respective steps 425 that is received by 110 in step442. Consider the example case depicted in FIGS. 2A, 2B, 2C. Looking atfrequency f₁, it can be seen that both sensor 105 and 115 detectedsignals, at 222 and 230 respectively. Sensor 110 did not detect a signalat that frequency—see sample 240. In such a case, sensor 110 mustaccount for the fact that two different sensors in the selected sensorgroup sent it in step 442 signal-related data. One non-limiting examplemethod for accounting for this situation is to have configuration datastored in storage 360 of sensor 110, for example, which indicate apriority order for choosing the detecting sensor. Another example methodis choosing the first signal received in step 442. Another examplemethod is performing an averaging calculation, or other similarcalculation that makes use of the data received from each of thedetecting sensors which sent data indicative of the entire received datasample at the detecting sensors—in this case, for example, data 222 and230.

In step 448, the detecting and identifying processor 340 ofnon-detecting sensor 110 may take assistance information, e.g. the dataindicative of the entire data sample received from the detecting sensors105 and/or 115 corresponding to the emitted signal which was detected bythem (e.g. corresponding to 222, 230, or some calculation based onthem), and also non-detecting sensor 110's own data indicative of theentire data 240 received during the corresponding defined time interval(e.g. dwell N), corresponding to that same emitted signal which wasdetected by sensors 105 and/or 115. The processor may utilize theassistance information to extract, from the data indicative of theentire data of the frequency band, that was received by thenon-detecting sensor during the corresponding defined time interval,data indicative of the emitted signal received by the non-detectingsensor during the corresponding defined time interval. For example, theprocessor may calculate difference data associated with the two sets ofdata, involving differential parameters such as TOA, Doppler or phase,using known techniques. Such a difference data result is an example ofdata indicative of the emitted signal received by the non-detectingsensor 110 during that corresponding defined time interval. In someexample cases, the process of calculating the difference data mayinvolve detection of the emitted signal by the non-detecting sensor 110.It may be said that the non-detecting sensor used the assistanceinformation to perform an assisted detection.

The extraction of data, as disclosed with reference to step 448, may bean example of the non-detecting sensor performing an action with respectto data indicative of an entire data of the frequency band received bythe non-detecting sensor during a corresponding defined time interval,where the action corresponds to the emitted signal received by thenon-detecting sensor during the corresponding defined time interval.

In step 450, the detecting and identifying processor 340 ofnon-detecting sensor 110 may send the difference data to the systemcenter 140. Though not shown, the system center may take data receivedin steps 433 and 450 to perform the application task, for example todetermine the geographic location of an emitter such as 120.

In steps 452, 454, 456, 461, 462, and 457, 460, non-detecting sensor 110may determine whether all frequency bins in the scanned frequency bandhave been analyzed, and act accordingly, in a manner detailed hereinregarding FIG. 4A.

In some example cases, a method such as disclosed with regard to FIG. 4Cmay have some advantage over a method such as disclosed with regard toFIG. 4A. For example, in the method disclosed in FIG. 4A, thenon-detecting sensor 110 may have to save buffered data, such as datareceived during the corresponding defined time interval, indicative ofthe at least one emitted signal detected by the at least one detectingsensor during the defined time interval, until communication to thesystem center is available. Such data may be buffered in Recorder #2365. In some examples of the method disclosed in FIG. 4C, thenon-detecting sensor 110 may calculate difference data, and send that onin step 450 when communication with the system center is available,without having to buffer after the calculation the above data receivedduring the corresponding defined time interval. The non-detecting sensormay in some cases buffer only the difference data. The non-detectingsensor may not be required to buffer data samples until communication tothe system center is available, while still being able to performextraction of the data indicative of the at least one emitted signal.This may be one example of data reduction achievable using the methodsof the presently disclosed subject matter.

Turning to FIGS. 5A and 5B, there is illustrated one example of ageneralized flow chart diagram of providing assistance informationbetween sensors, in accordance with certain embodiments of the presentlydisclosed subject matter. The method described with regard to FIG. 5 hassimilarities to the method described with regard to FIG. 4C. As such,much of the flow chart may be similar, and elaboration will be providedmainly of the steps that may not be identical or similar.

The example flow 404 starts at 405. Steps 405, 410, 411, 415, 412, 417and 420 may be similar to that described with regard to FIG. 4A. Inresponse to the determination at step 420 being Yes, that the criterionwas met, indicated by flow arrow 422, proceed to Figure B (505, 520). Instep 523 the detecting and identifying processor 340 of the detectingsensor 105 may extract, from the data, relevant data. This may be data223 indicative of the entire received data of a frequency band ofinterest. In some cases this may be data indicative of that portion 222of the entire received signal that corresponds to the frequency band 220received by the detecting sensor during the defined time interval, whichincludes the detected signal. In some example cases, such relevant datamay include processed samples 222 indicative of the frequency f₁corresponding to sample detection at the detecting sensor. In someexample cases, such relevant data may include samples for timesindicative of those times corresponding to sample detection at thedetecting sensor.

In step 526, the detecting and identifying processor 340 of theprocessor 320 of the detecting sensor may measure or determineparameters of data extracted in step 523, that relate to detectedsignals. These parameters may be indicative of the detected emittedsignal, and may be indicative of Signal to Noise Ratio of the detectedemitted signal. For example, it may measure, calculate or estimate thepulse parameter set, corresponding to the frequency bin X and the dwellnumber N. In the case of a signal that is composed of multiplerepetitions of pulses, it may also determine these parameters for someor all pulses, and it may also determine the PRI, the number of pulsesand the average SNR across pulses.

In step 528, detecting and identifying processor 340 may send some orall of these parameters, determined in step 523, to some or all of theother sensors in the relevant selected sensor group. The parameters thatare sent may be referred to as first information indicative of thedetected emitted signal, that is sent prior to the step of sendingassistance information to the sensors that may require assistanceinformation.

In step 530, sensor 105 has received these same parameters, this samefirst information, indicative of detection of the same emitted signal byother sensors, from some or all of the other sensors in the selectedsensor group. It may compare its own parameters to those received fromthe other sensors, to determine which assistance information, if any,should be sent to each one of at least one of other sensors in theselected sensor group. For example, it may determine which sensors didnot send parameters, and thus should be assumed to not have detected theparticular signal and be considered non-detecting sensors. It may alsodetermine whether it received the signal at a higher magnitude or SNRthan the other sensors that detected. Note also, that in the case of asignal that is composed of multiple repetitions of a pulses, sensor 105may also measure these parameters for some or all pulses, and it mayalso determine PRI and average SNR across pulses.

In step 532, the detecting and identifying processor 340 of thedetecting sensor 105 may determine whether it detected the signal at thehighest SNR. In response to the result of the determination being Yes,that the criterion was not met, indicated by flow arrow 535, theprocessor 340 may, in some cases, send in step 536 the data describedwith respect to 425, only to those sensors that did not report detectingthat signal. In this sense, in step 532 the sensor 105 may havedetermined which assistance information, if any, should be sent to eachone of the other sensors in the selected sensor group. Note thatdetecting the signal at the highest SNR is one example criterion fordetermining which sensor should send assistance information per signal.In some example cases, where the signal is composed of multiplerepetitions of pulses, the number of repetitions may be another examplecriterion. For example, if sensor 105 detected only 3 pulses atmagnitude 10, but sensor 115 detected 40 pulses at a somewhat lowermagnitude of 9, the determination may be made that sensor 115 shouldsend assistance information for that signal.

Note that this determination may be done per frequency or frequency bin,and separately per defined time interval. Which sensors received, andwhich received at highest SNR, may vary per bin and per time interval.Referring to FIGS. 2A-2C, it may be seen that at time T1, sensor 105received the signal 222 of f₁ at a magnitude of about 10, while sensor115 received the same signal 230 at a magnitude of about 7, and sensor110 received the same signal 240 at a magnitude of about 2, which isunder detection level 217. In this case, only 105 will send data in step536, and it will send only to one sensor, 110. By comparison, regardingf₂, sensor 115 received it 232 at about a level of 5, while the othertwo sensors did not detect it at all (224, 242). In this case, 115 willsend data in step 536 to multiple sensors, 105 and 110. Regarding f₄,none of the sensors detected the signal (228, 236, 246), and thus nonewill send data in step 535. Note also that in the next time interval,T2, (FIGS. 2D-2F), the detection levels may be very different persensor. For example, in T2 the strongest detection of the signalcorresponding to f₁ may be by sensor 115 (see 260), and sensor 110 mayalso detect it (see 270), while now sensor 105 did not detect at all250. An example is also shown of f₂ in time T2, where all three sensorsin the selected sensor group detected the signal (252, 262, 272), andthus for that case none will send assistance information for f₂. For f₄,which was not detected at all in T1, now in T2 sensor 110 is thestrongest (see 256, 266, 276), and it will send to the other twosensors.

Note also that the depiction with regard to FIG. 2 is only anon-limiting example, to illustrate for example that at different pointsin time different sensors may detect different signals. The exampledepiction indicated that the emitter frequency fell into one frequencybin. However, in other cases, the emitter frequency may fall, forexample, into two frequency bins. Similarly, the example depiction wasthat at each time interval T1, T2 detection occurred at particularsensors. However, as will be seen further herein with reference to FIG.9A, for example, in some cases, a signal pulse may last for more thanone processing frame, and thus several intervals T1, T2 etc. may passuntil detection of a signal pulse is made.

Note also, that if the detecting sensor 105 received no firstinformation, regarding a signal that it detected, from any of the othersensors in the selected sensor group, it may determine that it, sensor105, detected the signal at the highest SNR.

In step 538, the detecting and identifying processor 340 of theprocessor 320 of the detecting sensor 105 may send data relevant to theparticular application to another system, e.g. to system center 140, forfurther processing. This relevant data may be, for example, all of thedata extracted in step 523, or some portion of that data. In some cases,it may for example be the pulse parameters set parameter for thedetected signal. Note that step 538 may occur before step 536, or inparallel, in certain examples.

In response to the determination 532 being “No”, that the criterion wasnot met, indicated by flow arrow 534, no special action is taken. Steps534 and 536, 538 then proceed to 540, 469. In steps 452, 454, 456, 461,462, and 457, 460, detecting sensor 105 may determine whether allwhether all frequency bins in the scanned frequency band have beenanalyzed, and act accordingly, in a manner detailed herein regardingFIG. 4A.

Returning to the decision point in step 420 of FIG. 5A, in response tothe determination at step 420 being No, that the criterion was not met,indicated by flow arrow 424, in step 440, the detecting and identifyingprocessor 340 of non-detecting sensor 110 may take no action regardingthe frequency bin and dwell N, and may wait regarding such action, untilit receives a transmission of signal-related data from other sensors inthe same group. In step 510, non-detecting sensor 110 may receive such atransmission, from only the strongest detecting sensor (e.g. the onewith the highest SNR), containing assistance information, containingrelevant data corresponding to a signal detected by the detectingsensor. This may include the data which was sent by detecting sensor105, in step 536.

The next steps, 445 and 450, may be identical or similar to steps 448and 450 in FIG. 4C. It may be said that the non-detecting sensor usedthe assistance information to perform an assisted detection.

In steps 452, 454, 456, 461, 462, and 457, 460, non-detecting sensor 115may determine whether all frequency bins in the scanned frequency bandhave been analyzed, and act accordingly, in a manner detailed hereinregarding FIG. 4A.

A possible advantage of the example depicted with regard to FIG. 5, ascompared to that depicted with regard to FIG. 4C, is that only thestrongest sensor will send the assistance information, and it will sendit only to those sensors that need it, that is to those sensors that didnot detect. This may yield a lower total utilization of the bandwidth ofthe inter-sensor communication 160. A case in FIG. 5 where the detectingsensor sends the first information to all of the other sensors in thegroup, in step 528, and not to only some of them, may in some cases bemore advantageous. This may be one example of data reduction achievableusing the methods of the presently disclosed subject matter.

It should also be noted here, that there may be cases where a sensor 105detects an emitted signal, but it does not detect the signal in a mannerthat enables it to perform parameter estimation. This may be one examplefactor in choosing the appropriate assistance information to send. Thus,in some examples the assistance information may include measured,calculated, estimated or otherwise determined parameters. In otherexamples, the assistance information may not include such parameters,but may include only, for example, samples of data and/or instructionsto other sensors to save receive data.

Turning to FIG. 6, there are illustrated generalized examplerepresentations of types of signals, in accordance with certainembodiments of the presently disclosed subject matter. In graph 605,signal 630 depicts, in a very generalized sense, a coherent signal. Thephase of the signal stays continuous. Pulses 620 are shown as well. Ingraph 610, signal 640 depicts a non-coherent signal. Note, for example,at points 642, 645, 648 that there are discontinuities in the signal.The phase changes at those point.

Note that the methods of all of the Figures in the presently disclosedsubject matter may be applicable, in example cases, to both coherent andnon-coherent signals.

Turning to FIG. 7A, there is illustrated one example of a generalizedflow chart diagram of providing assistance information between sensors,in accordance with certain embodiments of the presently disclosedsubject matter. The method described with regard to FIG. 7A may be aspecific implementation of the more general method described with regardto FIG. 4A. As such, much of the flow chart may be similar, andelaboration will be made mainly of the steps that may not be identical.In a non-limiting example case, the method of FIG. 7A may be utilized,if the signal is coherent. An example of coherent signal was describedherein with respect to FIG. 6.

The example flow 700 starts at 405. Steps 705, 710, 711, 715, 712, 717and 720 may be similar to that described with regard to 405, 410, 411,415, 412, 417 and 420 of FIG. 4A. In response to the determination atstep 720 being Yes, that the criterion was met, flow arrow 722, in step723 the detecting and identifying processor 340 of the detecting sensor105 may extract from the data indicative of the entire received data ofthe frequency band, relevant data corresponding to the defined timeinterval, e.g. to dwell N. This relevant data may include dataindicative of the emitted signal during the defined interval. In someexample cases, this may be data indicative of the entire data samplereceived by sensor 105 during the defined time interval, thatcorresponds to the detected emitted signal. For example, this may bedata indicative of the entire received data sample, that correspond totimes in which the signal was detected, and the times of those samples.The times of such samples may be considered a second defined timeinterval of the at least one detected emitted signal. These may be, forexample, samples created by sampler 330. In some example cases, thisdata may be data indicative of the entire received data sample,corresponding to the frequency or frequency bin of the detected signalduring the defined time interval. These may be, for example, processedsamples 222 created by signal processor 335.

In step 726, the detecting and identifying processor 340 of thedetecting sensor 105 may measure and calculate values of parameters thatcorrespond to the emitted signal that the sensor detected. In someexample cases, these parameters may include the frequency or frequencybin or frequency bins for which the emitted signal was detected, thepulse width (PW), the dwell number, time or times (e.g. TOA)corresponding to the one detected emitted signal (e.g. times duringwhich the emitted signal was detected), the Pulse Repetition Interval(PRI) and the number of pulses that were detected for that particularemitter. It may also measure magnitude-related parameters such as, forexample, SNR. Pulse width may refer to the time interval between theestimated beginning and ending of an emitted pulse that was detected.PRI may refer to the time interval between the beginning of consecutivepulses emitted by a particular emitter. It may be relevant, for example,in cases where the signal is a series of pulses with periodicrepetition.

It should also be noted that, for simplicity of exposition, thediscussion and figures herein assume a constant PRI. In some cases, thePRI value may vary between some or all consecutive pulses. In thatsense, the PRI parameter may be in fact a number of PRIs. The PRIparameter sent in assistance information (in step 728 below) may thus,in some cases, be several PRIs, or a range of PRI values for the signal,or an average PRI, or a PRI with a tolerance. Similarly, the discussionassumes constant PW. In cases where PW is not constant, the PWparameters may be several PWS, or a range of PW values for the signal,or an average PW, or a PW with a tolerance.

The sensor may also measure modulation-related parameters. It may alsoestimate the accuracy of some or all of the parameters. Note that someof these parameters may be sent within a pulse parameters set.

In step 728, the detecting and identifying processor 340 of thedetecting sensor 105 may send, to one or more other sensors in theselected sensor group, assistance information. This information may insome cases include one or more sets, of some or all of the parametervalues, measured and calculated in step 726. In some examples, thisassistance information will be sent by sensor 105 to all of the othersensors in the sensor group. Note that in some examples, the sending ofcertain measured parameters is not necessary. For example, if theassistance information includes the TOA of the first pulse, and each ofthe PRIs between pulses, there may be no need to send the parameter“number of pulses”—since the sensor that receives the assistanceinformation can calculate this. For example, if the assistanceinformation includes the TOAs of each pulse, there may be no need tosend the parameter(s) PRI—since the sensor that receives the assistanceinformation can calculate this.

It should be noted here, that this assistance information that consistsof such parameter values, rather than of portions of received samples,is of a narrower bandwidth than data 223 corresponding to the entirefrequency band 220. The size of the data associated with the parametervalues may in some cases be less than 5000 bits per signal per dwell.The size of the data associated with the parameter values may in somecases be less than 1000 bits per signal per dwell. The size of the dataassociated with the parameter values may in some cases be less than 500bits per signal per dwell. The inter-sensor communication interface 160may thus be considered to require a relatively narrow bandwidth, ascompared to communication interfaces which must carry the entire datasample 223. This may be one example of data reduction achievable usingthe methods of the presently disclosed subject matter.

In step 733, the detecting and identifying processor 340 of theprocessor 320 of the detecting sensor 105 may send data relevant to theparticular application to another system, e.g. system center 140, forfurther processing. This relevant data may be, for example, the datasent to other sensors in step 728, or some portion of that data. In somecases, it may be other parameters. Note that step 733 may occur beforestep 728, or in parallel, in certain examples.

In steps 752, 754, 756, 761/762 (E), and 757, 760, detecting sensor 105may determine whether all whether all frequencies or frequency bins inthe scanned frequency band have been analyzed, and act accordingly, in amanner detailed herein regarding steps 452, 454, 456, 461, 462, and 457,460 of FIG. 4A.

Returning to the decision point in step 720, in response to thedetermination at step 720 being No, that the criterion was no met, flowarrow 724, in step 740, the detecting and identifying processor 340 ofnon-detecting sensor 110 may take no action regarding the frequency binX and dwell N, and may wait regarding such action, until it receives atransmission of assistance information from other sensors, possiblysensors in the same selected sensor group. In some examples, if noassistance information is sent within a configured time interval, sensor110 may delete or discard the relevant data that it buffered in steps715 and/or 717.

In step 742, non-detecting sensor 110 may receive such a transmission,from at least one detecting sensor, containing assistance information,containing parameter values corresponding to a signal detected by thedetecting sensor. This may include the parameter values which were sentby detecting sensor 105, and possibly others, in step 728.

In the next step, 746, the non-detecting sensor makes use of theassistance information parameters, to perform an assisted detection. Ifonly one detecting sensor 105 sent data in 728 that was received in 742,the basis for the step 746 may be the data sent from 105. In some cases,it is possible that more than one detecting sensor, e.g. both 105 and115, may send data in their respective steps 728 that is received by 110in step 742. In such a case, sensor 110 must account for the fact thattwo different sensors in the selected sensor group sent itsignal-related parameters in step 728. One non-limiting example methodfor accounting for this situation is to have configuration data storedin storage 360 of sensor 110, for example, which indicate a priorityorder for choosing the detecting sensor. Another example method ischoosing the first signal received in step 442. Another example methodis choosing the assistance information indicative of greatest SNR. Inother examples, accuracy will also be considered. Another example is toassign weights to each aspect, to score the assistance information fromeach, and to choose based on scoring.

The assistance information received in 728 may in some cases be utilizedto extract, from the data indicative of the entire data of the frequencyband received by sensor 110 during the defined time interval, dataindicative of the emitted signal received by it during the defined timeinterval. This extraction of data may include determining at least aTime of Arrival (TOA) value of the emitted signal at the non-detectingsensor. This TOA may be an example of data indicative of the emittedsignal received by the non-detecting sensor 110 during that defined timeinterval. Note also that in some example cases, e.g. cases of a repeatedsignal, there may be more than one Time of Arrival.

In some example cases, this determination may involve performing actionsto filter out noise in the data indicative of the entire data of afrequency band received by sensor 110, thereby detecting the emittedsignal. In some examples, elaborated on further herein, the actions tofilter out noise may involve integrating a portion, of the dataindicative of the entire data of the frequency band, that corresponds tothe emitter frequency, and corresponds to time intervals correspondingto the detected emitted signal. The emitter frequency, and these timeintervals, may be known from the assistance information.

The extraction of data, as disclosed with reference to step 746, may bean example of the non-detecting sensor performing an action with respectto data indicative of an entire data of the frequency band received bythe non-detecting sensor during a corresponding defined time interval,where the action corresponds to the emitted signal received by thenon-detecting sensor during the corresponding defined time interval.

In step 748, the detecting and identifying processor 340 ofnon-detecting sensor 110 may in some examples calculate or determinedifference data, involving differential parameters such as TOA, Doppleror phase, using known techniques, based on the outputs of step 746 andthe parameter values that it received in 742. In the case of forexample, geo-location, this differential data may be used to locate theemitter.

Such a difference data result is an example of data indicative of theemitted signal received by the non-detecting sensor 110 during thatdefined time interval. In step 750, the detecting and identifyingprocessor 340 of non-detecting sensor 110 may send the difference datato the system center 140. It may also send the TOA and/or otherparameters value(s). Though not shown, the system center may utilizedata received in steps 733 and 750 to perform the application task, forexample to determine the geographic location of an emitter such as 120.

In steps 752, 754, 756, 761/762 (E), and 757, 760, non-detecting sensor110 may determine whether all frequencies or frequency bins in thefrequency band have been analyzed, and act accordingly, in a mannerdetailed herein regarding steps 452, 454, 456, 461, 462, and 457, 460 ofFIG. 4A.

A possible advantage of the example depicted with regard to FIG. 7A, isthat in some example cases, neither of these sensors will have to sendsample data. They may send only parameters. In such a case, acomparatively small amount of data is sent by both detecting sensor 105in 728 and non-detecting sensor 110 in 750. Such communication willrequire data links of a comparatively narrower bandwidth, and similarlywill require less processing power and buffering to achieve thecommunication. This may be one example of data reduction achievableusing the methods of the presently disclosed subject matter.

Non-limiting exemplary methods of determining TOA will now be described.Turning first to FIG. 7B, a generalized exemplary representation offrequency bins is shown, according to some examples of the presentlydisclosed subject matter.

The non-limiting example disclosed herein will assume a samplingfrequency f equal to 1 Ghz, corresponding to a sample every Dt=1nanosecond (ns). This may be for example the frequency of sampling bysampler 330. The receiver functionality 315, using for example signalprocessor 335, may process these samples separately in groups of, forexample, n=128 samples each. In a case where signal processor 335performs, for example, Fourier Transform or digital filtering on thesamples, thus deriving processed samples in the frequency domain, theresult may be data points in frequency bins. Example graph 700 showssuch frequency bins. The number of bins produced by a filter may beequal to n (which is 128, in the example). The bandwidth of eachfrequency bin may be equal to (f_(s)/2)/n (see reference 730). This maybe the resolution of the frequency of a detected emitted signal.Therefore, references herein to emitter frequency may in some examplesrefer to emitter frequency bin. Note that the filtering may produce adata point in each bin, for each n-samples group in the time domain. Inthe example discussed herein, the frequency of the emitted signal may bein bin #2. Dt may be referred to herein as a data point spacing timeinterval.

Non-detecting sensor 110 may make use of at least several of theparameters received in step 728, to perform actions to filter out noisein the data indicative of the entire data of a frequency band receivedby sensor 110, thereby detecting the emitted signal. Examples ofparameters, which may be utilized advantageously in this way may includethe frequency bin of the emitted signal (e.g. bin #2 in graph 700), thepulse width PW, and the fact that a signal is repetitious and may have aPRI. In some examples, where the emitted signal is coherent, thenon-detecting sensor may also make use of that fact. Examples of the useof these parameters will elaborated on further herein.

Turning to FIG. 8, a generalized example of arranging filtered datapoints is presented, according to some examples of the presentlydisclosed subject matter. Taking the output of digital filtering,performed perhaps by signal processor 335, and arranging in the timedomain the filtered results for only one frequency bin, for example bin#2 of FIG. 7B, a graph such as 850 may be derived. Example points 831,833, 835, 837, all roughly of a certain magnitude, are plotted againstthe time axis, as are example points, 840, 842, 844, 846, all roughly ofa certain larger magnitude. Note that the points are plotted at times128, 256, 384 ns etc. This is because each point was derived fromfiltering performed of 128 time samples of 1 ns each, in the exampledisclosed herein. In, for example, the flow depicted in FIG. 7A, thismay represent the output of signal processor 335 of non-detecting sensor110, e.g. in step 711. These arranged data points may be used in furtherprocessing of the data. For example, in step 742, sensor 110 may havereceived parameters sent as assistance information by detecting sensor105. This may in some cases include parameters such as pulse parametersset, in some cases sent in step 728, that include the frequency bin ofthe signal detected at 105. Sensor 110 may use this frequency bininformation to analyze those data points in time that correspond to thefrequency bin of the signal. Note that, by ignoring frequency bins forwhich 105 did not report signal detection, sensor 110 may be filteringout noise. However, in some cases, the magnitude of the data points maystill be below the detection level 852, such that the signal has notbeen detected at sensor 110—despite the fact that these pointscorrespond to the frequency of the emitted signal. The gap between thehigher-power data points 840, 842, 844, 846 and the detection level isexemplified by 854. Points after time 1024 ns may exist, though they arenot shown for clarity reasons.

Some techniques to further filter out noise, and possibly detect thesignal, are now presented. These techniques may be performed, forexample, by detecting and identifying processor 340 of the processor 320of sensor 110, in some cases working together with other components suchas, for example, controller processor 374.

Turning to FIG. 9A, a generalized example of a signal in the time domainis presented, according to some examples of the presently disclosedsubject matter. The non-limiting example signal depicted in graph 905 ispulse 920. The pulse lasts roughly a time interval known as Pulse Width(PW). Note that there are points in time where there is a pulse, andothers with no pulse. Though not shown, the same pulse may be emittedagain by the emitter after a time known as the Pulse Repetition Intervalfrom the start of pulse 920. Sensor 110 may have received the value PWin the assistance information in step 742. Non-detecting sensor 110 maytake advantage of this information to assist it in a method to attemptto detect the signal, as will now be exemplified.

Considering graph 905, it may be understood that if sensor 110 performsa set of first integrations, on consecutive groups of data points intime, e.g. such as consecutive groups of the data points in graph 850,based on a first integration time interval T_(first) that corresponds toa defined percentage of the Pulse Width, the result may be first datapoints. In some cases, first integration time interval T_(first) mayalso be referred to herein as a first data point spacing time interval,as the first data points of an integration such that which results ingraph 950 will be spaced by T_(first).

Certain of such first data points may be derived from integration ofdata points that entirely or partly are times in which sensor 110received an emitted signal (although the sensor may have not detectedthe signal above the noise). Such first data points would havecomparatively high energy levels. On the other hand, others of the firstdata points may be derived from integration of data points in graph 850that entirely are times in which sensor 110 did not receive an emittedsignal. Since such other data points may contain only noise, theirintegration may yield first data points with comparatively low energylevels.

In choosing a value of first integration time interval T_(first), sensor110 may balance several considerations. On the one hand, a large valueof this interval may result in integrating a larger number of points,yielding higher energy levels and a greater probability of detection. Onthe other hand, it should be considered that integration of data pointswhich all, or nearly all, correspond to signal, would result in thehighest possible energy values as compared to integration of data pointsthat contain only noise. Therefore, choosing a large value of firstintegration time interval may cause integration of data points in graph850, within one group, where some data points contain signal and somecontain only noise. Such a choice would not yield the highest possibleenergy values. In some cases, first integration time intervals equal tovalues such as PW/3, PW/4, PW or even somewhat larger than PW, mayprovide acceptable results. The present exposition will continue withthe non-limiting example first integration time interval value of PW/2,which may in many cases provide a good balance between the aboveconsiderations.

N will be defined here as the number of data points in time that yield atime interval equal to, or just below, the first integration timeinterval Tint. Each first integration will be performed on N datapoints. Since each first data point corresponds to n samples,T_(first)−N*n*Dt=N*n/f_(s). In the example case where T_(first)−PW/2,this givesN=floor((PW/2)/(n*Dt))

Reverting to FIG. 8, the example case shown is of PW=1024, and firstintegration time interval T_(first) equal to PW/2=512 ns. In this case,we get N=512 ns/(1 ns*128 samples)=4 data points. Thus, the firstintegrations are performed in this case separately on consecutive groupsof four points. The first integration may be performed first on points831, 833, 835, 837, spaced 128 ns apart and thus covering a firstintegration time interval of 512 ns=PW/2. The first integration may beperformed next on points 840, 842, 844, 846, also spaced 128 ns apartand thus also covering a first integration time interval of 512 ns. Sucha first integration may be performed in this case also for some or allof the consecutive groups of four points, covering some or all of thedata points for frequency bin #2 that were output by signal processor335.

Non-limiting example filtering techniques for performing the firstintegrations include Fourier Transform, Fast Fourier Transform, DiscreteFourier Transform and a Finite Impulse Response (FIR). These are knownin the art. In some cases, such integrations may yield a gain of N.Other filtering techniques known in the art may be used.

Note that the non-limiting numeric examples above are presented only forease of exposition and of display on the graphs. In some cases, valuesof N larger than 4 may be expected to enable improved filtering results.

It may be said that detecting and identifying processor 340 of sensor110 is performing first integrations, of the data indicative of theentire data of a frequency band received by the sensor during thedefined time interval (e.g. dwell N), based on a first integration timeinterval and on the frequency bin corresponding to the emitterfrequency, and that these first integrations create first data points.The first integration time interval corresponds to a defined percentageof the Pulse Width.

It should also be noted, that in some example cases, prior to performingthe set of first integrations, detecting and identifying processor 340of sensor 110 may multiply the data indicative of the entire data of thefrequency band received by it, by a window. Examples of suitable windowsare Hamming, Chebyshev, or other windows known in the art. In somecases, the data indicative of the entire data of the frequency band maybe the processed samples generated by signal processor 335.

Turning to FIG. 9B, a generalized example of arranging filtered datapoints is presented, according to some examples of the presentlydisclosed subject matter. Graph 910 presents an example of such firstdata points. First data point 982, positioned at 512 ns, is the resultof the first integration of the four points 831, 833, 835, 837, whichranged from 0 to 512 ns. First data point 984, positioned at 1024 ns, isthe result of the first integration of the four points 840, 842, 844,846, which ranged from 512 to 1024 ns. First data points 986, 988, 989are the results of the first integration of three consecutive groups offour points that are not shown in graph 850. Graph 850 has, in theexample presented, N times as many points as does graph 910, in theexample four times as many, while the time intervals of points graph 910are thus four times that of those in graph 850.

The integration has also caused the magnitudes of the points of graph910 to be larger than that of those in graph 850. The processing gainfor this integration may in some examples be N. Comparing FIGS. 9A and9B, it can be seen that first data point 982 positioned at 512 ns is theresult of integration of data points that contain region 922, containing¼ of the pulse, as well as data points for times before 922 that containno signal. Similarly, first data point 986 positioned at 1536 ns is theresult of integration of data points that contain region 920, containing¼ of the pulse, as well as data points for times after 922 that containno signal. These two first data points are thus shown with magnitudevalues of approximately “5”. By comparison, first data point 984positioned at 1024 ns is the result of integration of data points thatcontain region 924, containing ½ of the pulse, and contain only datathat is indicative of the pulse. The region 924 contains no data pointsthat contain no signal, and no data points that contain only noise. Thisdata point is thus shown with a magnitude value of approximately “10”,larger than “5”. It can thus be seen that integrating N groups, suchthat integration on some of the groups may be on only data points thatcontain emitted signals, may increase the energy of the first datapoints, thus bringing the signal closer to possible detection.Considering first data points 988, 989, corresponding to times 2048 and2560 ns during which there was no signal pulse in 905, it may be seenthat they were derived from the integration of noise-only data points.988 and 989 thus have comparatively a very low magnitude, exemplified ingraph 910 as “0.1”. Again, other points after time 2560 ns are notshown, for clarity.

At this stage, sensor 110 may determine whether the first data pointsinclude data indicative of at least one emitted signal received by it.In some example cases, this first integration may be sufficient to raiseat least one first data point above the detection level 960, thusenabling detection by non-detecting sensor 110 of the emitted signal142. In such a case, the sensor 110 will determine that the first datapoints comprise data indicative the emitted signal received at sensor110. This may be referred to as an assisted detection. In other examplecases, even a high-energy first data point such as 984 may still bebelow the detection level 960, as exemplified by the gap 987. In suchcases, sensor 110 may perform additional actions to detect the signal,for example as presented further herein.

It should be again noted, that all the numbers presented here are onlyexamples for exposition. Similarly, graph 905 shows a pulse occurringover a period of time, such that exactly ¼ of it falls in each of twofirst data integrations and ½ of it falls in another first dataintegration. This of course is only presented as an example, since inother example cases the time alignments between pulse and firstintegration groups may not be as shown.

As indicated above, in some example cases, sensor 110 may determine thatthe first data points do not comprise the data indicative of the emittedsignal of which sensor 105 reported in 728. In response to such adetermination, sensor 110 may perform additional actions to detect thesignal, making use of the assistance data. It may, for example performadditional filtering on the data of graph 910 of FIG. 9B to boost thesignal levels to possibly above the detection level. In some examples,this additional filtering may be based on the PRI parameter. As anon-limiting example, the emitter may work at a 10% duty cycle. Giventhe example value of PW=1024 ns, PRI may be in such a case be 10,240 ns.Also, in this example, the number of signal pulses sent by the emitterduring the current dwell is 100 pulses.

Turning to FIG. 10, a generalized example of arranging filtered datapoints is presented, according to some examples of the presentlydisclosed subject matter. FIGS. may show a conceptual rearrangement ofthe first data points in graph 910, a rearrangement which may be usefulfor performing additional filtering. For example, graph 1000 of FIG. 10Ashows point 1006, identical to point 982, positioned at 512 ns. The nextfirst data point on graph 1000 is 1008, which corresponds to time 512+the value of the PRI for the signal. This first data point 1008 appearsin 910, far to the right of point 989, but is not shown in graph 910,for clarity reasons. Next shown in 1000 is the first data point 1012,which corresponds to time 512 ns+2 times the value of the PRI. This maybe continued, for time 512 ns+3*PRI and so on, until the final firstdata point on graph 1000, point 1014, corresponding to 512 ns+(M−1)times the value of PRI. M−1 is the number of second integration timeintervals, a term which will be explained further herein. There are Mfirst data points in each graph of FIG. 10. For convenience, each firstdata points point on each graph can be referred to as point m, where m=1to M.

In some cases, M may be equal to the number of signal pulses sent by theemitter during the current dwell. Note that the points between 2*PRI and(M−1)*PRI are not shown in 1000, nor in 910, for clarity.

Similarly, FIG. 10B shows an example arrangement 1005, of first datapoints from 910, arranged by the interval of PRI, in a manner similar tothat of 1000, but this time starting with first data point 1022corresponding to first data point 984, positioned at 1024 ns. FIG. 10Cshows a similar example arrangement 1010, of first data points from 910,but this time starting with first data point 1041 corresponding to firstdata point 986. FIG. 10D shows a similar example arrangement 1020, offirst data points from 910, but this time starting with first data point1051 corresponding to first data point 988. Similar graphs may becreated for all first data points in 910 up to the time equal to PRI, inthe example case equal to 10,240 nanoseconds. In this manner, all firstdata points on 910 may be rearranged based on the PRI value, in thisexample.

Considering FIG. 10, it can be seen that each graph may correspond to anexample arrangement of first data points from 910, arranged by a seconddefined interval, referred herein to as second integration timeinterval. In the example of FIG. 10, this second integration timeinterval may be the PRI. In this example, K may be defined as the numberof first integration time intervals that are equal to, or nearly equalto, one second integration time interval:K=floor(second integration time interval/first integration timeinterval)

One second integration time interval would comprise K first integrationtime intervals, but no more. For the example numbers presented here, Kmay be the number of PW/2 intervals that fit into one PRI. Forconvenience, the first data points that fit into one PRI may be referredto herein as points k=1 to K. Recall that M−1 is the number of secondintegration time intervals. M is equal to the number of points to beintegrated in each second integration. In some cases, M may be equal tothe number of signal pulses sent by the emitter during the currentdwell. Thus, the total number of first data points across all of thesecond integration time intervals may be K*M. It may thus also be seenthat FIG. 10A contains all the first data points for which k=1, FIG. 10Bcontains all the first data points for which k=2, FIG. 10C contains allthe first data points for which k=3, and so on. A graph not shown inFIG. 10 would show all first data points for which k=K.

In the case shown in FIG. 10, each point on a particular graphcorresponds to the same portion of the repeated pulse. For example, allof the points in graph 1000 correspond to the first, partial, portion ofthe pulse 920, as depicted in graph 905 as region 922 corresponding to512 ns and its repetitions. This may be the case if the spacing used inthe rearrangement is exactly equal to the PRI. Thus all of the points1006, 1008, 1012, 1014 are in the vicinity of magnitude “5”. Similarly,all of the points in graph 1005 correspond to the second, full, portionof the pulse, containing all signal, as depicted in graph 905 as region924 corresponding to 1024 ns and its repetitions. Thus all of the points1022, 1024, 1026, 1028 are in the vicinity of magnitude “10”. Recallfrom the discussion of FIG. 9 that this relatively high magnitude may bedue to the fact that in some cases these points may all be points thatcontain signals. Similar comparisons can be made between graph 1010,region 926, and the approximate magnitude “5”. Similar comparisons canbe made between graph 1020 and the region of graph 910 corresponding to2048 ns, in which there is no signal and only noise, and the approximatemagnitude is “0.1”.

Taking FIG. 10 as the basis for understanding a possible process, anexample process for filtering to increase signal SNR is now described.Non-detecting sensor 110 may perform a set of second integrations, ofdata indicative of the first data points (exemplified in graph 910),based on a second integration time interval T_(second) that correspondsto the Pulse Repetition Interval. The example shown in the figures usesPRI as the value of the second integration time interval T_(second).

Each set of second integrations may be done on a second group, of firstdata points, such that at least two conditions are fulfilled:

(1) Each second group starts with a “starting point”, which is a uniqueone of the first data points represented by graph 910 that range between0 ns (representing the beginning of the first data points) and a timeequal to the second integration time interval (equal to PRI, in theexample case presented here). Recall from the discussion above thatthere are K such starting points, with relative positions k=1 to K.

(2) Each second group includes all, or some, of the first data pointsrepresented by graph 910 that are spaced an integral number of secondintegration time intervals from each other. In some examples, there maybe M such first data points in each group. In in the example casepresented here, these points in each group will be spaced a PRI fromeach other.

Non-limiting example filtering techniques for performing these secondintegrations include Fourier Transform, Fast Fourier Transform andDiscrete Fourier Transform. These are known in the art. In some cases,such integrations may yield a total gain of N*M for the first and secondintegrations. Other filtering techniques known in the art may be used.

A difference between the first and second integrations should be noted,in some example cases. The first integrations are performed onconsecutive groups of data points, where each first integration isperformed on a group that is composed of N consecutive data points,which cover a time approximately equal to a first integration timeinterval. By contrast, the second integrations are performed on secondgroups, where each second group is composed of points that are NOTconsecutive, but rather are spaced from each other by a secondintegration time interval. The second integration may be based onnon-consecutive first data points. The starting points of each secondintegration may be consecutive. There are up to K such starting points.Thus, in some examples, the first integration time interval may be aninterval of consecutive points which are integrated, while the secondintegration time interval may be the interval at which the various firstdata points to be integrated are spaced, the interval between pointsthat are sampled for the second integration.

Note that the rearrangement of FIG. 10 can in some examples be done by avalue of second integration time interval T_(second) other than the PRI.The rearrangement may be by a different value, that corresponds to, oris close to, the PRI value (smaller or larger than PRI). For example,the second integration time interval could be 2*PRI.

Note also that the preceding is only one non-limiting exampleimplementation. The second integrations may in some cases be performedwith respect to all K starting points. In some cases, the secondintegrations may be performed with respect to only some of them.Performing all K second integrations may in some cases improve theprobability of signal detection. The second integrations may in somecases be performed with respect to M equal to all pulses emitted by theemitter, while in some cases it may not be performed with respect to allemitted pulses.

Turning to FIG. 11, a generalized example of second data points ispresented, according to some examples of the presently disclosed subjectmatter. FIG. 11 may show a result of such a set of second integrations,performed with respect to first data points of FIG. 10. Graph 1100 showsonly data for frequency bin #2, in which the emitted signal was detectedby detecting sensor 105. In the example, second data point 1111 is theresult of a second integration performed on the second group consistingof first data points of graph 1000, starting at 512 ns and counting insteps of PRI. Similarly, second data point 1113 is the result of asecond integration performed on the second group consisting of firstdata points of graph 1005, starting at 1024 ns and counting in steps ofPRI. Second data point 1115 corresponds to graph 1010, and startingpoint 1536 ns; while Second data point 1117 corresponds to graph 1020,and starting point 2048 ns. In the example of graph 1100, the secondintegration time interval is equal to PRI, M is equal to the number ofpulses (which in the example is 100 pulses), and second integrationswere done over all M−1 second integration time intervals. Recalling theearlier definition of K, time 512 ns in this example is 1/K* the PRI,1024 ns=2/K*PRI, while the time 10,240 ns of the last point is=K/K*PRI,equals one full PRI.

Thus, in some example cases, detecting and identifying processor 340 ofthe non-detecting sensor 110 may have performed a second integration, ofdata indicative of the first data points, based on a second integrationtime interval, and on the at least one frequency bin corresponding tothe at least one emitter frequency, thereby creating second data points,where the second integration time interval corresponds to the PulseRepetition Interval. This was done to determine a Time of Arrival valueof the emitted signal at the non-detecting sensor.

The result of such second integrations may be to further boost the SNRof the signal. This may give, in some examples, a total N*M as comparedto the original processed samples—where N is the number of data pointsper group used in the first integration, and M−1 is the total number ofsecond integration time intervals. Graph 1100 exemplifies results for anexample of 100 pulses, and integration on all pulses. In this case,M=100. A case in which the second integrations were performed on data ofall pulses would increase this gain. In the graph 1100, second datapoint 1113 has a magnitude close to 1000, M=100 times the magnitude ingraph 1005. A similar example gain can be seen for second data points1111 and 1115, with magnitudes of roughly 500, as compared to themagnitudes in graphs 1000 and 1010. These second data points in somecases may now also above the detection level 1107. On example of the gapis shown in 1145.

Next, the maximum power would be determined. In the example of graph1100, this would be second data point 1113. The time 1024 nscorresponding to 1113 may thus be determined to be the TOA of the firstpulse, within a certain resolution. This approximate TOA calculation maybe TOA=k*N*n/f_(s), where k=1 to K is the relative position of the TOAwith respect to the PRI, with K as defined above, and f_(s) is thesampling frequency of e.g. sampler 330. Note that in the non-limitingexample of graph 1100, k=2 gives the maximum power.

In such cases, detecting and identifying processor 340 may havedetermined that the second data points comprise the data indicative ofthe emitted signal received by non-detecting sensor 110, and thus thepulse has been detected.

In this example, the first pulse has been determined to occur somewherebetween approximately between 512 ns and 1024 ns. The PW may be used todetermine the approximate time boundaries of the pulse. TOA of the firstpulse may thus have been determined. It may be said, in such a case,that the non-detecting sensor used the assistance information to performan assisted detection. Also, other pulses may be known to start atinteger PRI intervals from the TOA of the first pulse, and end at theM-th pulse. Thus, in some cases all pulses may have been detected, andmore than one TOA may have been determined.

Note also that the second data points 1117, 1119 etc. in this example,derived from processed samples corresponding only to sample times withnoise only and no signal, still have relatively low magnitudes, belowthe detection level 1107—and thus such second data points clearly do notrepresent times of signal pulses.

It should be noted, that if the emitted signal is a coherent one, thefirst and second integrations may raise the energy level, and increasethe SNR, of the relevant data points, more than in a non-coherentcase—and thus in some cases such integrations may have a higherprobability of enabling detection in the case of a coherent signal.

In some example cases, the first integrations may be performed on allfrequency bins of the integration previous to it. Similarly, in someexample cases, the second integrations may be performed on all frequencybins of the integration previous to it. In other example cases,depending on the resolution of bandwidth of the emitted frequency whichthe detecting sensor send in step 728 as part of the parameters of theassistance information, the method may be more selective as to whichfrequency bins should be integrated in either or both of the first andsecond integrations.

It should also be noted, that in the above examples the firstintegrations are performed on processed samples that in some cases maybe derived by signal processor 335, by for example performing digitalfiltering on samples received from sampler 330. In these examples, N isequal to 4 data points, each spaced 128 ns apart, and the N pointsencompass a first integration time interval of 512 ns. However, in otherexamples, non-detecting sensor 110, e.g. utilizing its detecting andidentifying processor 340, may instead perform the first integrations onthe samples received from sampler 330. For the example values presentedherein, these first integrations would be on consecutive groups of4×128=512 points, each spaced 1 ns apart. N in such a case is equal to512, rather than 4. Note that the first integration time intervalremains 512 ns. In such cases, the samples received from sampler 330 mayconstitute the data indicative of the entire data of a frequency bandreceived by the at least one non-detecting sensor during thecorresponding defined time interval, on which the first integrations areperformed.

It should also be noted, that an example case was presented, ofperforming first integrations, and then performing second integrationsonly if the first integrations did not result in signal detection. It isenvisioned that in other example cases, second integrationscorresponding to, for example, PRI may be performed first, directly onthe data points of the processed samples. In such a case, only if thesecond integrations did not result in detections, first integrationscorresponding to, for example, PW may be performed.

In some examples, if a more accurate TOA is desired than is obtainableusing the above methods for the particular application and systemarchitecture 100, additional steps may be performed, to provide in somecases a more accurate TOA. Now that the TOA of each detected pulse isknown, within a certain resolution, the first and second sets ofintegrations may be performed again on, for example, the processedsamples obtained from signal processor 335. However, in this examplerepetitions of the above integrations, three changes may be incorporatedin the first integrations.

First, the first integration time interval may be set equal to PW,rather than for example a value such as PW/2 or PW/3 used to determinethe rough TOA value(s). That is, the first integrations may be performedon something close to 2*N data points. This may improve the resultingSNR. In some cases, the first integration time interval may be set toanother value close to the PW but not equal to it.

Second, rather than performing first integrations on distinctconsecutive groups of N data points, a first integration may beperformed on partially overlapping groups. That is, in some examples afirst integration will be performed on a particular data point X and the2*N data points following it, another first integration will beperformed on data point X+1 (adjacent to data point X) and the 2*N datapoints following it, and so on, until the data point that is positioned2*N data points before the end of the third defined time interval(described below). Note that in some example cases, such an approachcould have been taken also to find the initial values of TOA, but it maybe considerably less efficient than the example method disclosed withrespect to FIGS. 8 to 11.

Third, once the TOA or TOAs are known, the need to integrate data pointscorresponding to the possibly long periods of time in which no signalwas emitted may in some examples be obviated. For example, given a 10%duty cycle, 90% of the data points may contain no signal. By skippingthese points, this process can be done more efficiently. Thus, theintegrations can be performed only with respect to that portion of thedata which corresponds to a time that is within a second time intervalbefore the Time of Arrival of each detected pulse (which was calculatedfor sensor 110), and a third time interval after this Time of Arrival.This may be especially advantageous, where 2*N data points are beingintegrated, in respect of each data point within the second and thirdtime intervals. In one non-limiting example, the second and third timeintervals could both be 2*PW. The data points within these intervalsaround each pulse TOA would constitute data indicative of an entire dataof the frequency band received by the non-detecting sensor during thedefined time interval.

First integrations performed using the above variations may be referredto herein as modified first integrations. Their output first data pointsmay be referred to as modified first data points. The updated TOAvalue(s) may be referred to as second Time(s) of Arrival.

Using such a method, the TOA(s) of the pulse may in some cases bederived with greater accuracy, possibly due to the finer resolution ofthe single-point moving of groups of points and the improved SNR.

Turning to FIGS. 12A and 12B, there is illustrated one example of ageneralized flow chart diagram 1200 of determining TOA(s), in accordancewith certain embodiments of the presently disclosed subject matter. Themethod described with regard to FIG. 12 may in some examples cases be aspecific implementation of step 746 in FIG. 7A. The methods exemplifiedin FIG. 12 may in some example cases make use of the methods elaboratedherein with respect to FIGS. 7B through 11. In some example cases thesteps may be performed by detecting and identifying processor 340 of anon-detecting sensor 110.

Turning first to FIG. 12A, the process may start at 1203. In step 1205,the value of the first integration time interval may be set to a definedpercentage of the Pulse Width. The pulse width may have been reported asa parameter by e.g. detecting sensor 105, for example in step 728. Instep 1210, first integrations may be performed on data indicative of theentire data of the frequency band received by the non-detecting sensorduring the defined time interval. These integrations may be based on thefirst integration time interval and on emitter frequency. For example,the integrations may be based on the frequency bin corresponding to theemitter frequency. The output of the first integrations may be firstdata points 1215.

In step 1220, a determination may be made, whether the first data pointscomprise data indicative of the emitted signal received by thenon-detecting sensor. In response to the determination being Yes, theTOAs may be derived, for example as elaborated further herein, and theprocess may end 1290.

In response to the determination being No, in step 1225 the value of thesecond integration time interval may be set, to correspond to the PulseRepetition Interval. The PRI value may have been reported as a parameterby e.g. detecting sensor 105, for example in step 728. In step 1230,there may be performed second integrations, of data indicative of thefirst data points, based on the second integration time interval, and onthe emitter frequency. The output of the second integrations may besecond data points 1235.

In step 1240, a determination may be made that the second data pointscomprise data indicative of emitted signal received by the non-detectingsensor. TOAs may be derived, for example as elaborated further herein.

In step 1245, a determination may be made whether the accuracy of thecalculated TOA(s) is sufficient for the needs of the particularapplication.

In response to the determination being Yes, the process may end 1290.The updated TOA value(s) may be referred to as second Time(s) ofArrival.

In response to the determination being No, flow may continue (1250,1255, F) to FIG. 12B. In step 1260, the value of the first integrationtime interval may be set in some examples to the Pulse Width, or in someexamples to a value close to the Pulse Width.

In step 1265, the detecting and identifying processor 340 may select,from data indicative of the entire data of the frequency band receivedby non-detecting sensor, a portion of the data which corresponds totimes that are within a second time interval before, and a third timeinterval after, the Times of Arrival.

In step 1270, the detecting and identifying processor 340 may performmodified first integrations, of the portion of the data, based on thefirst integration time interval and the emitter frequency. These firstintegrations may be performed separately in respect of each of the dataindicative of the entire data. This process may create modified firstdata points 1273.

In step 1275, steps 1225, 1230 and 1240 may be performed, where themodified first data points are considered first data points in step1230. The updated values of TOA may be determined, possibly moreaccurate than those determined earlier in the flow.

This process may end at 1280. The updated TOA value(s) may be referredto as second Time(s) of Arrival.

It should be noted here, that the above example cases all disclose adetecting sensor sending assistance information to a non-detectingsensor, and that in some cases they may use other systems as a relay.However, in other example cases, the detecting sensor 105 may insteadsend the assistance information to one or more system centers 140. Theassistance information may in some examples be one or more of thosedescribed with regard to the various flow chart Figures. The systemcenter may be configured to receive such assistance information from oneor more detecting sensors 105, 115. It may analyze and process thisdata. In some cases the system center 140 may compare data received frommultiple detecting sensors, for example determining which of themdetected the signal at the highest SNR. The system center may haveconfiguration data regarding the system regarding the specificapplication task to be performed. In some cases, based on the analysisof the assistance information, and on configuration data, the systemcenter may send second assistance information to the non-detectingsensor 110.

In some cases, the second assistance information and the firstassistance information may be the same. In some cases, the secondassistance information may be one or more of those described with regardto the various flow chart Figures, which is not identical to the firstassistance information that the system center received from one or fromany of the detecting sensors. For example, the assistance informationmay include a certain amount of data indicative of data received by thedetecting sensor(s), sent in some cases because the detecting sensor(s)did not have the processing capacity to determine parameters based onthe data. The system center, possessing in some cases greater processingcapacity, may be able to derive the parameters and send those as thesecond assistance information. In another example, the system center mayextract from the assistance information only a sub-set of the data, andsend that reduced subset as the second assistance information to thenon-detecting sensor 110.

An example advantage of such an implementation is that the system center140 may have more processing and storage capacity than any or all of thedetecting sensors 105, 115. Another example advantage of such animplementation is that the system center 140 may have access to updatedor additional data from sources external to the system. The systemcenter may thus, in some cases, be able to make a moreapplication-appropriate decision what is the best assistance informationthat should be sent to non-detecting sensors such as 110. Also, asindicated above, in some cases this decision may lead to the sending ofa smaller amount of data to the non-detecting sensor 110, compared tothe amount of data sent by detecting sensor 105 to system sensor 140.

In some embodiments, one or more steps of the various flowchartsexemplified herein may be performed automatically. The flow andfunctions illustrated in the various flow chart figures may for examplebe implemented in processing circuitry 350, and may make use ofcomponents described with regard to FIGS. 3A and 3B.

It is noted that the teachings of the presently disclosed subject matterare not bound by the flow charts illustrated in the various figures. Theoperations can occur out of the illustrated order. For example, it wasnoted that operations 421 and 430 shown in succession can be executedsubstantially concurrently or in the reverse order. This applies also,for example, to steps 424 and 432, 425 and 433, among others. Similarly,some of the operations or steps can be integrated into a consolidatedoperation or can be broken down to several operations, and/or otheroperations may be added. It is also noted that whilst the flow chart isdescribed with reference to system elements that realize them, such asfor example processing circuitry 350, this is by no means binding, andthe operations can be performed by elements other than those describedherein.

In embodiments of the presently disclosed subject matter, fewer, moreand/or different stages than those shown in the figures can be executed.In embodiments of the presently disclosed subject matter one or morestages illustrated in the figures can be executed in a different orderand/or one or more groups of stages may be executed simultaneously.

In the claims that follow, alphanumeric characters and Roman numeralsused to designate claim elements are provided for convenience only, anddo not imply any particular order of performing the elements.

It should be noted that the word “comprising” as used throughout theappended claims is to be interpreted to mean “including but not limitedto”.

While there has been shown and disclosed examples in accordance with thepresently disclosed subject matter, it will be appreciated that manychanges may be made therein without departing from the spirit of thepresently disclosed subject matter.

It is to be understood that the presently disclosed subject matter isnot limited in its application to the details set forth in thedescription contained herein or illustrated in the drawings. Thepresently disclosed subject matter is capable of other embodiments andof being practiced and carried out in various ways. Hence, it is to beunderstood that the phraseology and terminology employed herein are forthe purpose of description and should not be regarded as limiting. Assuch, those skilled in the art will appreciate that the conception uponwhich this disclosure is based may readily be utilized as a basis fordesigning other structures, methods, and systems for carrying out theseveral purposes of the present presently disclosed subject matter.

It will also be understood that the system according to the presentlydisclosed subject matter may be, at least partly, a suitably programmedcomputer. Likewise, the presently disclosed subject matter contemplatesa computer program product being readable by a machine or computer, forexecuting the method of the presently disclosed subject matter or anypart thereof. The presently disclosed subject matter furthercontemplates a non-transitory machine-readable or computer-readablememory tangibly embodying a program of instructions executable by themachine or computer for executing the method of the presently disclosedsubject matter or any part thereof. The presently disclosed subjectmatter further contemplates a non-transitory computer readable storagemedium having a computer readable program code embodied therein,configured to be executed so as to perform the method of the presentlydisclosed subject matter.

Those skilled in the art will readily appreciate that variousmodifications and changes can be applied to the embodiments of theinvention as hereinbefore described without departing from its scope,defined in and by the appended claims.

The invention claimed is:
 1. A system capable of communicating information concerning a received signal, comprising: a sensor, the sensor comprising a processing circuitry and configured to: (a) responsive to receiving by at least one detecting sensor, during a defined time interval, data indicative of an entire data of a frequency band received by the at least one detecting sensor during the defined time interval, comprising at least one signal emitted by at least one emitter, and to detecting of the at least one emitted signal by the at least one detecting sensor, performing one of the following: A. send from the at least one detecting sensor assistance information corresponding to the at least one emitted signal detected by the at least one detecting sensor during the defined time interval, to at least one non-detecting sensor; or B. send from the at least one detecting sensor, to at least one system center, assistance information corresponding to the at least one emitted signal detected by the at least one detecting sensor during the defined time interval, wherein the assistance information is capable of being utilized by the at least one system center to send second assistance information to at least one non-detecting sensor, wherein the assistance information comprises at least one set of parameter values corresponding to the least one detected emitted signal, wherein the at least one set of parameter values comprises at least one of: one or more emitter frequencies; at least one pulse width (PW); at least one Time of Arrival corresponding to the least one detected emitted signal; at least one Pulse Repetition Interval (PRI); a number of pulses, wherein the assistance information and the second assistance information are capable of being utilized by the at least one non-detecting sensor to perform an action with respect to data indicative of an entire data of a frequency band received by the at least one non-detecting sensor during a corresponding defined time interval, the action corresponding to the at least one emitted signal received by the at least one non-detecting sensor during the corresponding defined time interval, wherein the performing of the action comprises extracting, from the data indicative of the entire data of a frequency band received by the at least one non-detecting sensor during the corresponding defined time interval, data indicative of the at least one emitted signal received by the at least one non-detecting sensor during the corresponding defined time interval, wherein the extracting of the data indicative of at the least one emitted signal comprises determining at least a Time of Arrival (TOA) value of the at least one emitted signal at the at least one non-detecting sensor, said at least the Time of Arrival of the at least one emitted signal constituting data indicative of at least one emitted signal received by the at least one non-detecting sensor during the corresponding defined time interval.
 2. The system of claim 1, wherein said determining at least the Time of Arrival value comprises performing actions to filter out noise in the data indicative of an entire data of a frequency band received by the at least one non-detecting sensor, thereby detecting the emitted signal, wherein the actions to filter out the noise comprise integrating a portion of the data indicative of an entire data of a frequency band that corresponds to at least one emitter frequency and wherein the portion of the data corresponds to time intervals corresponding to the at least one detected emitted signal.
 3. The system of claim 1, wherein the at least one set of parameter values comprises modulation-related parameters.
 4. The system of claim 1, wherein the size of the at least one set of parameter values, corresponding to one emitter and to one dwell, is less than 1000 bits.
 5. The system of claim 1, wherein the at least one signal emitted by the at least one emitter is a coherent signal.
 6. A system capable of performing an action associated with a received signal, comprising: a sensor, the sensor comprising a processing circuitry and configured to: (a) perform one of the following: A. receive by at least one non-detecting sensor, an assistance information from at least one detecting sensor; or B. receive second assistance information from at least one system center, the second assistance information sent in response to the at least one system center receiving assistance information from the at least one detecting sensor, wherein the assistance information is capable of being utilized by the at least one system center to send the second assistance information, wherein the assistance information was sent by the at least one detecting sensor, responsive to receiving by the at least one detecting sensor, during a defined time interval, data indicative of an entire data of a frequency band received by the at least one detecting sensor during the defined time interval, comprising at least one signal emitted by at least one emitter, and to detecting of the at least one emitted signal by the at least one detecting sensor, wherein the assistance information and the second assistance information correspond to the at least one detected emitted signal detected by the at least one detecting sensor during the defined time interval, wherein the assistance information comprises at least one set of parameter values corresponding to the least one detected emitted signal; and (b) perform the action with respect to data indicative of an entire data of the frequency band received by the at least one non-detecting sensor during a corresponding defined time interval, the action corresponding to the at least one emitted signal received by the at least one non-detecting sensor during the corresponding defined time interval, wherein the performing of the action comprises extracting, from the data indicative of the entire data of a frequency band received by the at least one non-detecting sensor during the corresponding defined time interval, data indicative of the at least one emitted signal received by the at least one non-detecting sensor during the corresponding defined time interval, wherein the extracting of the data indicative of the at least one emitted signal comprises determining at least a Time of Arrival (TOA) value of the at least one emitted signal at the at least one non-detecting sensor, said at least the Time of Arrival of the at least one emitted signal constituting data indicative of at least one emitted signal received by the at least one non-detecting sensor during the corresponding defined time interval, wherein said determining at least the Time of Arrival value comprises performing actions to filter out noise in the data indicative of an entire data of a frequency band received by the at least one non-detecting sensor, thereby detecting the emitted signal, wherein the actions to filter out the noise comprise integrating a portion of the data indicative of an entire data of a frequency band that corresponds to at least one emitter frequency and wherein the portion of the data corresponds to time intervals corresponding to the at least one detected emitted signal.
 7. The system of claim 6, wherein the assistance information comprises at least one set of parameter values corresponding to the least one detected emitted signal, wherein the at least one set of parameter values comprise at least one of: one or more emitter frequencies; at least one pulse width (PW); at least one SNR; at least one Time of Arrival corresponding to the least one detected emitted signal; at least one Pulse Repetition Interval (PRI); a number of pulses; modulation-related parameters.
 8. The system of claim 6, wherein the at least one signal emitted by at least one emitter is a coherent signal.
 9. The system of claim 6, wherein said actions to filter out noise comprise: i) performing at least one first integration, of the data indicative of the entire data of a frequency band received by the at least one non-detecting sensor during the corresponding defined time interval, said first integration based on a first integration time interval and on the at least one emitter frequency, thereby creating first data points, wherein the first integration time interval corresponds to a defined percentage of the at least one Pulse Width; and ii) determining whether the first data points comprise the data indicative of at least one emitted signal received by the at least one non-detecting sensor.
 10. The system of claim 9, wherein the first integration time interval is equal to PW/2.
 11. The system of claim 9, wherein the first integration is one of a Fourier Transform, a Discrete Fourier Transform, a Fast Fourier Transform and a Finite Impulse Response (FIR).
 12. The system of claim 9, wherein the data indicative of the entire data of a frequency band received by the at least one non-detecting sensor is multiplied by a window prior to step (i).
 13. The system of claim 9, wherein the size of the at least one set of parameter values, corresponding to one emitter and to one dwell, is less than 1000 bits.
 14. The system of claim 9, the system further configured to: iii) in response to determining that the first data points do not comprise the data indicative of at least one emitted signal, perform a second integration, of data indicative of the first data points, based on a second integration time interval, and on the at least one emitter frequency, thereby creating second data points, wherein the second integration time interval corresponds to the at least one Pulse Repetition Interval; and iv) determine that the second data points comprise the data indicative of at least one emitted signal received by the at least one non-detecting sensor.
 15. The system of claim 14, wherein the second integration is based on the number of pulses.
 16. The system of claim 14, wherein the second integration time interval is based on the at least one Pulse Repetition Interval (PRI).
 17. The system of claim 16, wherein the second integration time interval is equal to the at least one Pulse Repetition Interval (PRI).
 18. The system of claim 14, wherein the second integration is one of a Fourier Transform, a Discrete Fourier Transform and a Fast Fourier Transform.
 19. The system of claim 14, the system further configured to: (v) set the second integration time interval to be equal to the at least one Pulse Width, (vi) select, from the data indicative of the entire data of a frequency band received by the at least one non-detecting sensor, a portion of the data which corresponds to a time that is within a second time interval before at least one Time of Arrival of the at least one emitted signal at the at least one non-detecting sensor, and a third time interval after the at least one Time of Arrival, constituting data indicative of the entire data of a frequency band received by the at least one non-detecting sensor during the corresponding defined time interval; (vii) perform at least one modified first integration, of the portion of the data, said first integration based on a first integration time interval and on at least one emitter frequency, thereby creating modified first data points, wherein the first integration time interval corresponds to the at least one Pulse Width, wherein first integrations are performed separately in respect of each of the data indicative of the entire data of a frequency band received by the at least one non-detecting sensor, wherein the modified first data points constitute first data points; and (viii) repeat said steps (iii) and (iv), thereby determining a second Time of Arrival value of the at least one emitted signal.
 20. The system of claim 19, wherein the second Time of Arrival value is more accurate than the Time of Arrival value. 